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Magnetoelectric coupling, dielectric and electrical properties of xLa0.7Sr0.3MnO3 – (1−x) Pb (Zr0.58Ti0.42)O3 (x = 0.05 and 0.1) multiferroic nanocomposites
Accepted Manuscript Magnetoelectric coupling, dielectric and electrical properties of xLa0.7Sr0.3MnO3 – (1−x) Pb (Zr0.58Ti0.42)O3 (x = 0.05 and 0.1) multiferroic nanocomposites S.K. Mandal, Swati Singh, Rajesh Debnath, A. Nath, P. Dey PII:
S0925-8388(17)31876-5
DOI:
10.1016/j.jallcom.2017.05.259
Reference:
JALCOM 41990
To appear in:
Journal of Alloys and Compounds
Received Date: 5 March 2017 Revised Date:
6 May 2017
Accepted Date: 25 May 2017
Please cite this article as: S.K. Mandal, S. Singh, R. Debnath, A. Nath, P. Dey, Magnetoelectric coupling, dielectric and electrical properties of xLa0.7Sr0.3MnO3 – (1−x) Pb (Zr0.58Ti0.42)O3 (x = 0.05 and 0.1) multiferroic nanocomposites, Journal of Alloys and Compounds (2017), doi: 10.1016/ j.jallcom.2017.05.259. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Magnetoelectric Coupling, Dielectric and Electrical Properties of xLa0.7Sr0.3MnO3 – (1-x) Pb (Zr0.58Ti0.42)O3 (x = 0.05 and 0.1) Multiferroic Nanocomposites
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S. K. Mandal*, Swati Singh, Rajesh Debnath and A. Nath Department of Physics, National Institute of Technology Agartala, Agartala, Tripura, 799046, India P. Dey
Abstract
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Department of Physics, Kazi Nazrul University, Asansol, 713304,W.B., India
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We have investigated magnetoelectric coupling, dielectric and electrical properties of xLa0.7Sr0.3MnO3(LSMO)– (1-x) Pb(Zr0.58Ti0.42)O3 (x = 0.05 and 0.1) nanocomposites, prepared through low temperature pyrophoric reaction process. Magnetoelectric response has been detected in these multiferroic nanocomposites at room temperature attributing the presence of magnetostriction properties of piezomagnetic material. Noticeably, all nanocomposites are found to exhibit room temperature ferroelectric behavior. Studies of dielectric constant of those
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nanocomposites reveal the Maxwell Wagner interfacial polarization at low frequency regime. The ac electrical properties of nanocomposites have been studied employing impedance spectroscopy technique. The value of impedance has been found to decrease with increase in
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magnetic field attributing to the depinning of LSMO domain walls at the grain boundaries pinning centres and thereby enhancing the spin dependent transport mechanism in the composites. Impedance study at different temperatures shows temperature dependent electrical
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relaxation process in the system. The activation energy is estimated from Nyquist plots, dc and ac conductivity data using the Arrhenius relation. This is indicating that the same type of charge carrier is responsible for both the relaxation and the conduction processes in the system. Ac conductivity curves follow a Jonscher’s double power law. The conduction mechanism in temperature is mainly due to the small and large polaronic hopping in the system.
Key words: Magnetoelectric coupling, Multiferroic, Nanocomposites. *
Corresponding author: Tel: +913812348530 E-mail address:[email protected] (S. K. Mandal) 1
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I. INTRODUCTION Magnetoelectric (ME) coupling is a process of combining spontaneous magnetization and
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ferroelectric polarization simultaneously in a single system. ME materials have fascinated many researchers for their ability to perform different functions simultaneously. They are promising candidates for potential use in memory based devices, such as in spintronics and magnetic field sensors applications. In ME materials, the induced polarization (P) is directly proportional to the
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applied dc magnetic field (H) as P = αH, where α is the second rank ME-susceptibility tensor.
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The term α is determined by measuring δP in an applied ac magnetic field (δH). ME voltage coefficient, αE = δE/δH is directly related to α by an expression as α = εoεrαE, where εo and εr is the free space permittivity and relative permittivity of the material, respectively [1]. There is very less material available in nature, such as BiFe2O3, which exhibits ME effect in single phase. However, the effect is restricted at very low temperature and hence such material is not
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promising for commercial applications. This fact has motivated many researchers to initiate synthesis and study of multiferroic composites, films and multilayers in order to obtain enhanced ME effect at room temperature. Multiferroic nanocomposites, exhibiting ME effect have
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triggered intense research interest from past few years due to its probable applications in
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magnetic field sensors [2], multiple – state memories [3], data – storage devices [4] etc. In composite systems, ME effect is an extrinsic property [5], which derives from ME
coupling between the magnetic and piezoelectric phases. Thus, in order to achieve a relatively strong ME signal from multiferroic ME composites, the two basic requirements are : (1) a high piezoelectric material and (2) a strong magnetic material [6, 7]. Outstanding piezoelectricity of Lead zirconate titanate (PZT) and excellent magnetostriction of lanthanum strontium manganese oxide (LSMO) [8] make them appealing as good candidates for ferroelectric and ferromagnetic 2
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phases, respectively, in such multiferroic composites where we can expect strong ME effect at room temperature. Z.
H.
Tang
et
al.
have
reported
enhanced
ME
response
for
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La0.67Sr0.33MnO3/PbZr0.52Ti0.48O3 bilayer thin film at room temperature, prepared through pulsed laser deposition method [9]. C. A. F. Vaz et al. have shown ME response of Pb(Zr0.2Ti0.8)O3/La0.8Sr0.2MnO3 multiferroic heterostructures [10]. J. B. Huarac et al. have
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studied ME response and magneto-dielectric properties of Ba0.7Sr0.3TiO3/La0.67Sr0.33MnO3 bifunctional nanocomposites, prepared through high temperature solid state reaction technique
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[11]. M. Kumar et al. have reported large magnetoresistance of La0.67Sr0.33MnO3-BaTiO3 nanocomposite, prepared through sol – gel method [12]. Z. Duan et al. have shown ME response of layered composite film of Pb(Zr0.52Ti0.48)O3/La0.67Sr0.33MnO3, prepared through a chemical solution deposition method [13]. P. Martins et al. have investigated magneto-dielectric effect of
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series of xCoFe2O4/(1-x)PVDF nanocomposites, where x = 20% sample shows highest magnetodielectric effect [14]. R. Brito-Pereira et al. have shown ME response increasing with increase in Terfenol –D, contained in Terfenol –D/P(VDF-TrFE) composite [15]. P. Martins et al. have
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reported maximum ME response for 30 wt% of Terfenol-D in Terfenol-D/CoFe2O4/P(VDFTrFE) composite, prepared through solvent casting technique [16]. N. Adhlakha et al. have
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studied structural, dielectric, magnetic and ME effect of (1-x)(0.3CoFe2O4-0.7BiFeO3)-xPVDF nanocomposites film, prepared through hot press method, where they have shown maximum ME response for x = 0.4 samples [17]. T. Zheng et al. have shown piezoelectric response of PVDF/Fe3O4 composite nanofibers and confirms a nanoscale ME effect using Piezoresponse Force Microscopy technique [18]. Ch. Thirmal et al. have investigated magneto-dielectric response of PVDF - La0.7Sr0.3MnO3 polymer nanocomposite thick film, fabricated by dip coating
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technique [19]. High ME coupling effect have been reported for Metglas/PMN-PT laminate composites [20]. F. Yan et al. have investigated ME coupling in C-axis oriented
[21]. In
our
study,
we
have reported
ME
effect
in
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La0.67Sr0.33MnO3/PbZr0.52Ti0.48O3 films, fabricated by sol-gel method on LaAlO3 (00l) substrates
xLa0.7Sr0.3MnO3(LSMO)
–
(1-x)Pb(Zr0.58Ti0.42)O3 (PZT) (x = 0.05 and 0.1) perovskite multiferroic nanocomposites at room
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temperature. ME coefficient (αE) as a function of dc magnetic field has been studied for 0.1LSMO – 0.9PZT composite at a frequency of 1kHz and for 0.05LSMO – 0.95PZT composite
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at 2 kHz in both transverse and longitudinal configurations. Moreover, magneto-dielectric studies give evidence of ME effect in all those composites. Dielectric study of those nanocomposites gives the evidence of Maxwell Wagner interfacial polarisation at low frequency region at different applied magnetic field. Furthermore, we have carried out complex impedance
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properties of nanocomposites at room temperature with varying magnetic field. Nyquist plots are fitted using parallel combinations of resistance – capacitance circuit showing dominant effect of grain boundary pinning centre in the system. Apart from the magnetic field dependence, the
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effects of temperatures on dielectric and electrical properties have also been investigated. Nyquist plots reveal temperature dependent electrical relaxation process in the system.
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Furthermore, the activation energy is estimated from relaxation time, dc conductivity and ac conductivity of those nanocomposites. II. EXPERIMENTAL DETAILS Multiferroic nanocomposites xLSMO – (1-x)PZT (x = 0.05 and 0.1) have been prepared by low temperature chemical “pyrophoric reaction process”[22 -27] and solid state route. The LSMO phase were prepared from high-purity La2O3 (Alfa Aesar, 99.99%), Sr(NO3)2(Merck, 4
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99.0%) and Mn(CH3COO)2 (Merck, 99.0%). The required amount of La2O3, Sr(NO3)2.9H2O, Mn(CH3COO)2 and Ho(NO3)2 were mixed in a distilled water. All the nitrates and acetate were soluble in distilled water. Then the solution is heated at ~180̊C for few minutes with continuous
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stirring. After some time, TEA was added in the solution with metal ions maintaining the ratio 4:1:1 (TEA :La,Sr: Mn). After adding TEA, the solution became viscous and colloidal. The metal ions were precipitated in the solution. At the same temperature, HNO3 was added to
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dissolve the precipitation and then the clear solution was evaporated with constant stirring. After complete dehydration, the nitrate themselves were decomposed with the evolution of brown
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fumes of NO2 leaving behind a voluminous, organic based, brownish black, fluffy powder known as precursor powder. The precursor powder was mechanically grinded, and then calcined at temperatures of 800 ̊C in air for 5 hours to get nanocrystalline powders. The chemical reaction
Mn+ + N(CH2CH2OH)3 (Metal ion = La,Sr, Mn)
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involved in the preparation of LSMO nanopowder is as follows:
(Metal ion – TEA complex)
M2On+ CO2+H2O
1800C
O + + H2O
M – H2C O
Calcination
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+ Co2 +NO2 + C
[M – N(CH2CH2OH)3]n+
(n-1)+
(Nano sized composite powder)
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After preparation of LSMO nanoparticles, we have mixed it with requisite amount of PZT powder (purchased from APC International Ltd. USA) for 10 hrs. Then the mixed powder has been again calcined in air for 5 h at a temperature of 8000 C to obtain the required nanometric composite phase. We have made circular pellets from calcined nano powders and have sintered them for 30 minutes. The sintering temperatures were same as that of calcination temperatures for all those nanocomposites. Then these pellets have been used for electrical measurements. We
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have done electrode on the sample surface using high temperature silver paste and have used two probes measurement technique. For ME measurement we have poled the electrode samples. After poling we have used 42 gauge copper wire as an electrical leads.
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Structural characterization has been done by X-ray diffraction technique (XRD) (Bruker D8 Advanced) with monochromatic Cu-Kα radiation. For ME measurement, we have used ME measurement setup comprising of electromagnet (Polytronic laboratory electromagnet, EM –
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100), electromagnet power supply (Polytronic power supply – CCP – 100Y), wide band power amplifier (Krohn – Hite corporation– 7500), lock – in amplifier (Stanford research system –
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SR830), Helmholtz coil, function generator and Keithley multimeter. The ME measurements have been carried out for two different field orientations: (1) transverse configuration where H and Hac are parallel and δE perpendicular to the sample plane. The ME coefficient in transverse configuration is represented by αE31 and (2) longitudinal configuration where H, δH and δE are
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perpendicular to the sample plane. The ME coefficient in longitudinal configuration is represented by αE33. The two configurations are shown in inset of Figs. 2 (a) and (b). The electrical characterizations have been carried out in LCR meter (HIOKI -3532-50 LCR
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HiTESTER) at different magnetic field. For electrical measurement, the magnetic field has been applied using an electromagnet (Nuis Technologies). Polarization-electric field measurements
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have done employing Sawyer –Tower circuit using mixed domain oscilloscope (Tektronix, MDO-3054).
III. RESULTS AND DISCUSSION A. RESULTS (a) Structural Characterization
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Structural characterization has been done through XRD technique at room temperature. The detailed study of XRD patterns of 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 1 (a) and (b), respectively. The average crystallite size (Φ)for
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0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZTnaocomposites has been calculated through XRD patterns using Scherrer formula as [28]: Φ= kλ/βeffcosθ
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where, Φ is the average diameter of the nanocrystals in Å, k is the shape factor, λ is the wavelength of CuKα radiation (1.542Å), θ the diffraction angle and βeff defined as
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βeff2= βm2-βs2
where,βm and βs are the experimental full width half maxima of the present sample and that of a standard silicon sample, respectively. The standard silicon sample is used to calibrate the intrinsic width associated with the equipment. The average crystallite size is found to (Φ ~ 41 nm
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±1 %) for LSMO phase, and (Φ ~ 31 nm ±1 %) for PZT phase for 0.05LSMO-0.95PZT nanocomposites, and (Φ ~ 42 nm ±1 %) for LSMO phase and (Φ ~ 29 nm ±1 %) for PZT phase for 0.1LSMO-0.9PZT nanocomposite. We have indexed the XRD peaks using JCPDS software
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and data sheet 49- 0595and 73 – 2022 for LSMO and PZT nanoparticles, respectively.
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(b) Magnetoelectric Coupling
αE as a function of H has been measured by swiping dc magnetic field from +H to -H and
-H to +H for all the nanocomposites. αE as a function of H at a frequency(f) of 2 kHz and 1 kHz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 2 (a) and (b), respectively. For x = 0.1 sample, during positive cycles αE31 gradually increases with H showing a peak at ~ 600 Oe, followed by a gradual decrease with further increase in H. During negative cycles of H, similar behavior has been observed but in negative direction. Similar 7
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behavior has also been observed for x = 0.05 sample but peak has been observed at a H of ~800 Oe, as shown in Fig. 2 (a).The value of αE31 is found to be ~ 0.95 mV/cmOe a ta H of ~ 600 Oefor 0.1LSMO – 0.9PZT and ~0.52 mV/cmOe at a H of ~ 850 Oe for 0.05LSMO – 0.95PZT
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nanocomposites. We have also measured αE33 as a function of H at a f of 2 and 1kHz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites, as shown in Fig. 2(b).Similar behaviors are found in αE33 vs. H curves for both the nanocomposites. The value ofαE33is found to
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~ 0.54 mV/cmOe at H of ~ 760 Oe for 0.1LSMO – 0.9PZTnanocomposite and ~ 0.36 mV/cmOe at H of ~ 970 Oe for 0.05LSMO – 0.95PZT nanocomposite. αE as a function of f has been carried
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out for 0.05LSMO – 0.95PZTnanocompositeat a H of ~ 800 Oe and for 0.1LSMO – 0.9PZT nanocomposites at a H of ~ 600 Oe, as shown in Fig. 2 (c) and 2 (d), respectively. αE shows a sharp peak at a f ~1kHz for 0.1LSMO – 0.9PZT and ~2 kHz for 0.05LSMO – 0.95PZT nanocomposites. For both the configurations, the observed variation of αE with H may be due to
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the variation of piezomagnetic coefficient with H of piezomagnetic material of the samples [29]. In presence of ac and dc magnetic field, a dynamic strain is produced in magnetic phase. This induced strain generates an electric field in piezoelectric phase giving rise to a ME effect in the
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sample [29].The magnitude difference in transverse and longitudinal magnetoelectric coefficient may be due to the directional dependence of the magnetostriction and piezomagnetic coefficients
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[1].Furthermore, room temperature polarization vs. electric field (P – E) loops for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites at a f of 10 Hz are shown in inset of Fig. 2 (d). This measurements show the room temperature ferroelectric behavior of nanocomposites. (c) Effect of Magnetic Field on Dielectric Study Dielectric constant (ε) as a function of f at different H for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites has been investigated, as shown in Figs. 3 (a) and (b), 8
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respectively.ε is found to decrease with increase in H and f for both nanocomposites. At high f region, ε curves at different H merge and behave as independent of f. Obtained ε at an absence of H for 0.1LSMO – 0.9PZT nanocomposite is found to be ~ 3 times greater than 0.05LSMO –
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0.95PZT nanocomposite at same f. In other words, ε increases with increase in LSMO content in the composites. Although, the decrease in ε on application of H for 0.1LSMO – 0.9PZT is quiet
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less as compared to 0.05LSMO – 0.95PZT nanocomposite. The high value of ε at low f region for all H is may be explained through the light of Maxwell Wagner interfacial polarization [30].
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Simultaneously, dielectric loss [tanδ] has been studied as a function of f for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites as shown in Figs. 3 (c) and (d), respectively. It is found that tan δ decreases with increase in H for both the nanocomposites. However, the change in tanδ value with respect to H is very less throughout the measured f range for
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0.01LSMO – 0.95PZT nanocomposites. For both the nanocomposites the value of tanδ is found to < 1.6.
Apart from dielectric measurements the observed ME effect is further verified by
(%) =
() () ()
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magnetodielectric (MD) study with H and f for those nanocomposites using the relation as MD × 100, where ε(Η) is dielectric constant in presence of H and ε(0) is the
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dielectric constant in the absence of H. The MD (%) as a function of H at a f of 1 and 2kHz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocompositesare shown in inset of Figs. 3 (a) and (b), respectively. The observed MD (%) for 0.05LSMO – 0.95PZT nanocomposites is found to ~ 10 times of 0.1LSMO – 0.9PZT nanocomposites. The observed positive MD (%) is may be due to decrease in grain boundaries resistance (Rgb) of the sample. The impedance (Z) is related to Rgb as [31,32]
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Z=
+
+
where, Rg is grain resistance, Rgb is grain boundaries resistance, Rele is electrode resistance, Cg is
sample. If we consider Cgb is very small as compared to Rgb then Z α Rgb
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grain capacitance, Cgb is grain boundaries capacitance and Cele is electrode capacitance of the
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In impedance study it is found that Rgb decreases with increase in H, which supports our
relation as ML (%) =
() () ()
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experimental observations. Simultaneously, magnetolosses (ML) have been estimated using the × 100, where, tanδ (Η) is dielectric loss in presence of H
and tanδ (0) is the dielectric loss in absence of H. The ML (%) vs. f curves for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in inset of Figs. 3 (c) and (d),
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respectively. The value of ML is found to increase with increase in H for 0.05LSMO – 0.95PZT nanocomposites; while it decreases with H for 0.1LSMO – 0.9PZT nanocomposites. This is due to the grain boundaries pinning center of ferromagnetic LSMO grains [33].
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(d) Effect of Magnetic Field on Impedance Spectroscopy The measured ME coupling of those nanocomposites is f dependent. Moreover, ac
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electrical properties give the f dependence of Rgb, Cgb, Rg and Cg of the nanocomposites. Thus, real and imaginary part of impedance for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are carried out at different Hs and temperatures. Temperature dependent impedance measurement is discussed later. Real part of impedance (Zˊ) as a function of f at different Hs for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites is shown in Figs. 4 (a) and (d), respectively. Zˊvs. f curves are found to gradually decrease with increase in f
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and become constant at higher f region for both the nanocomposites. Imaginary part of impedance (Z") as a function of f at varying H for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites is shown in Figs. 4 (b) and (e), respectively. Z′ vs. f curves are found to
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gradually decrease with increase in f at different applied H for both the samples. Similar behavior is observed for Z" vs. f curves for 0.05LSMO – 0.95PZT nanocomposites whereas a small change is observed with increase in H for 0.1LSMO – 0.9PZT nanocomposites. The decreased in
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impedance (Zˊ and Z") for 0.05LSMO – 0.95PZT nanocomposites is may be due to grain boundaries pinning center of ferromagnetic LSMO grains [33]. In case of ferromagnetic grains
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the domain walls get pinned at the pinning center of the ferromagnetic grains. When H is applied, depinning of LSMO grain from grain boundaries pinning center takes place due to which electronic scattering at the conduction band get enhanced. However, in case of 0.1LSMO – 0.9PZT nanocomposites the effect of both pinning and scattering process is may be same,
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which is corroborating the small change with H. Nyquist plots at varying H for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 4 (c) and (f), respectively. Nyquist plots have been fitted using parallel combinations of grain boundaries resistance (Rgb)
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and grain boundaries capacitance(Cgb) circuits as shown in inset of Fig. 4 (b).For both the nanocomposites two such parallel combinations of Rgb and Cgb circuits have been used; first Rgb1
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and Cgb1 circuit correspond to grain boundaries resistance and grain boundaries capacitance for LSMO grains and; second Rgb2 and Cgb2 circuit correspond to grain boundaries resistance and grain boundaries capacitance for PZT grains. The fitted parameters for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Table I. A significant decrease in Rgb1 and Rgb2 with increase in H is observed for both the nanocomposites. The value of Nyquist plots is found to decrease with increase in H for 0.05LSMO – 0.95PZT nanocomposites, which indicates
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that resistivity decreases with increase in H, whereas for 0.1LSMO – 0.9PZT nanocomposites the value of Nyquist plots is found to almost independent of H. The red solid lines in Figs. 4 show the fitting of the curves.
=
() () ()
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Furthermore, ac magnetoresistance (Rm) has been estimated using the relation as Rm (%) × 100, where R(Η) is ac resistance in presence of H and R(0) is the ac resistance in
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absence of H [34]. Rm as a function of H for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Fig. 5 (a) and (b), respectively. The value of Rm increases with
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increase in H and decreases with increase in f for 0.05LSMO – 0.95PZT nanocomposites. The maximum value of |Rm (%)| is found to ~ 25 % for 0.05LSMO – 0.95PZT nanocomposites and ~ 5 % for 0.1LSMO – 0.9PZT nanocomposites at a f of 73 Hz. Similarly, we have also estimated ac magnetoimpedance (Zm) using the relation as Zm (%) =
() () ()
× 100, where Z(Η) is an ac
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impedance in presence of H and Z(0) is an ac impedance in absence of H [34]. The Zm vs. H curves for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 5 (c) and (d), respectively. For both the nanocomposites, the value of |Zm (%)|increases with
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increase in Hand is found to maximum at af of 73 Hz. Also, we have calculated an ac magnetoreactance using the relation as Xm (%) =
() () ()
× 100, where X(Η) is an ac
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reactance in presence of H and X(0) is an ac reactance in absence of H [29]. Xm vs. H curves for0.05LSMO– 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites at different fs are shown in insets of Figs. 5 (c) and (d), respectively. For both the nanocomposites the value of Xm(%) increases with increase in H. The observed Rm, Zm and Xm are attributed to the change of permeability of the materials induced by the applied H. (e) Effect of Temperature on Dielectric Study
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ε as a function off at different temperatures for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 6 (a) and (b), respectively. ε increases with increase in temperatures for both the nanocomposites and the maximum value of ε at low f region is well
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explained through the light of Maxwell Wagner model[35]. According to this theory dielectric materials are formed by combinations of two layers; first layer is conducting in nature called as grain and second layer is non-conducting called as grain boundaries[35]. We believe that when
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temperatures is increased in the system. The conducting grains acquires sufficient amount of thermal energy in order to enhance the flow of charge carriers through the grain boundaries.
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Simultaneously, tan δ has been carried out for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites as shown in Fig. 6 (c) and (d), respectively. Similarly, tanδ also increases with increase in temperatures.
(f) Effect of Temperature on Impedance Spectroscopy
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Z′ as a function of f at different temperatures for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 7 (a) and (d), respectively. Insets in Fig. 7 (a) and (d) show the magnified view of Z′ vs. f curves at high temperature for 0.05LSMO – 0.95PZT and
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0.1LSMO – 0.9PZT nanocomposites, respectively. It has been observed that for both the nanocomposites the value of Z′ decreases with increase in temperatures. Furthermore, Z″ vs. f
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curves for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 7 (b) and (e), respectively. A sharp resonance peak is observed at high temperature region for both the nanocomposites. Moreover, it is observed that the value of Z′ and Z″ decreases with increase in LSMO content in the composites, which attributes more metallic nature in the composite. Nyquist plots for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 7 (c) and (f), respectively .Furthermore, Nyquist plots have been fitted using same circuit as
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shown in inset of Fig. 4 (b). Fitted parameters for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Table II. Rgb1 and Rgb2 are found to decrease with increase in temperatures for both the nanocomposites attributing enhanced flow of charge carriers through
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the grain boundaries of the nanocomposites. The normalized Z″/Z″o spectrum with f/fo are found to almost independent of temperatures as shown in Fig. 8, which indicates no temperature dependent broadening of the spectra, where, Z″o is impedance at resonance frequency and fo is
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the resonance frequency. The overlapping of curves at all the temperatures in a single curve further confirms a temperature independent dynamical process [36].As the magnitude of Z′ and
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Z″ for both the nanocomposites is found to decrease with increase in temperature having no peak broadening indicating temperature dependent Arrhenius type in the system. The activation energy is associated with the relaxation process, which is determined by the relation as [37,38]: 2πfoτ = 1
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where, τ is relaxation time. ln (τ) vs.103/T plots for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocmposites are shown in Figs. 9 (a) and (b), respectively. ln(τ) vs.103/T plots exhibit linear behavior, whereτ is found to decrease with increase in temperatures. This in turn, indicates
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temperature – dependent electrical relaxation process in the samples. τ is found to follow
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Arrhenius nature as [31, 37, 38]:
τ = τ exp O
!"
where, τ is the pre-factor, Ea is the activation energy for relaxation process and kβ is the O
Boltzmann constant and T is the absolute temperature. The estimated value of Ea for both the nanocomposites is found to be ~ 0.40(± 0.03) eV. The value of Ea is found to similar with the reported value of LSMO – PZT super lattice structure [31]. Moreover, the value of Ea has been
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further verified from dc conductivity (σdc) data. Some steps have been followed for such fitting. σdc has been calculated using the relation as [37 - 39]:
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σdc = t/RA where, t is the thickness of the sample, R is the bulk resistance and A is the area of the sample. In order to calculate R following relation has been used as [32, 34]: 2πfoRC = 1
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where, C is the capacitance of the sample at fo. ln (σdc) vs.103/T plots for 0.05LSMO – 0.95PZT
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and 0.1LSMO – 0.9PZT nanocmposites are shown in Fig. 9 (c) and (d), respectively. Both the curves exhibit linear behavior, where ln (σdc) is increasing with an increase in temperatures. Thus, conductivity process in the system increases with increase in temperatures, which indicates negative temperature coefficient of the resistance (NTCR) of the samples [38, 39]. σdc is found to follow the Arrhenius nature by the following relation as [36 - 38]:
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σdc = σoexp
!"
where, σo is the pre exponential factor and a characteristics of the material. The estimated value
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of Ea is found to similar with the obtained value from the relaxation process. This in turn, indicates that the same kind charge carriers are responsible for both relaxation and conduction
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process in the nanocomposites systems [38, 39]. (g) AC Conductivity
The f dependent ac conductivity (σac) at different temperatures for 0.05LSMO – 0.95PZT
and 0.1LSMO – 0.9PZT nanocmpositesis shown in Figs. 10 (a) and (b), respectively. The value of σac is calculated from dielectric data of respective samples using the relation as [31, 37 - 39]: σac = ωεοεtanδ
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where, ω is the angular f, εο is the vacuum dielectric constant. At low temperatures, the σac increases with increase in f for both the nanocomposites. As we know that the grain boundaries of dielectric material are formed from oxygen ions, which mean that each grain possesses
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oxygen rich layer on the surface of grain boundary. Such grains boundaries are active at low f region, which gives the less amount of flow of charge carriers through this boundaries. As we have increased the applied field the conducting grains become more active by promoting the
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flow of charge carriers through the grain boundaries[35]. However, at high temperature, the σac
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is found to independent off at low f region. Furthermore,σacvs. f curves show three different segments for 0.05LSMO – 0.95PZT nanocomposite at high temperature as shown in inset of Fig. 9 (a) [31]. Such observation is not observed for 0.1LSMO – 0.9PZT nanocmposites. These curves have been fitted using Jonscher’s double power law as[31]: σac = σdc + Aωn + Bωp
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where, the first term σdc corresponds to f independent region (segment I), which gives the dc conductivity of the system, the second term Aωn(segment II) where 0 < n < 1 signifies low f regime, which corresponds to short range translational hopping motion and the third term Bωp
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(segment III) where 1 < p < 2 signifies high f regime, which corresponds to localized or
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reorientation hopping motion. The n and p values obtained from the fitting data are shown in Figs. 11 (a) and (b) for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocmposites, respectively. For 0.05LSMO – 0.95PZT nanocomposites the value of n exhibits continuous decrease with increase in temperature whereas the value of p continuously increases with increase in temperatures. However, both the values of n and p are decreased with increase in temperatures for 0.1LSMO – 0.9PZT nanocomposites. Moreover, some literatures[40 – 42] have discussed the dependency of n and p on temperatures and f, where an increase in f the 16
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independent parameters (n and p) are raised with temperatures corresponding to small polaronic hopping, whereas as decreased in n and p is marked by large polaronic hopping. In the present scenario, for 0.05LSMO – 0.95PZT nanocomposites the conduction in segment II is determined
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by large polarons whereas in segment III is assisted by small polarons type hopping mechanism. Similarly, the conduction process is determined by large polarons hopping mechanism for 0.1LSMO – 0.9PZT nanocomposites.
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B. DISCUSSION
Study of room temperature ME coupling of those nanocomposites at different fs gives the
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evidence of magnetostriction properties in the samples. Also, these nanocomposites are found to exhibit room temperature ferroelectric behavior. The presence of such ME coupling is further supported by room temperature magnetodielectric study of all those nanocomposites. Furthermore, dielectric study at low f region shows the evidence of Maxwell Wagner interfacial
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polarization in presence of magnetic fields. Impedance study of those nanocomposites gives the evidence of grain boundary pinning center of the ferromagnetic LSMO grains. The observed ac magneto – resistance, impedance and reactance of both the nanocomposites are originated from
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change of permeability induced by applied H. Temperatures dependent dielectric properties of those nanocomposites give the evidence of Maxwell Wagner interfacial polarization.
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Temperatures dependent impedance study shows thermally assisted relaxation process in the system. Activation energy is estimated from both temperatures dependent τ and σdc, which indicates that same kinds of charge carriers are governing both the processes. σac as a function of f at different temperatures is found to obey double power law, which is attributed that different types of charge species are responsible for conduction process. IV. CONCLUSIONS 17
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In conclusions, xLSMO – (1-x)PZT (x = 0.05 and 0.1) nanocomposites have been prepared by a low temperature chemical pyrophoric reaction process and solid state route. (a) Detailed analysis of XRD patterns shows the simultaneous existences of both LSMO and
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PZT phases in the sample.
(b) The value of αE is found to ~ 0.95 mV/cmOe for 0.1LSMO – 0.9PZTnanocomposites at H of
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~600 Oe at a f of 1kHz in transverse configuration at room temperature. The observed ME effect may be due to the magnetostriction property of piezomagnetic material.
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(c) Analysis of P – E loop shows that 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are ferroelectric in nature at room temperature.
(d) Magnetodielectric study of those nanocomposites further confirms the existence of magnetocoupling effect in the sample.
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(d)Nyquist plots have been fitted using parallel combinations of grain boundaries resistance and grain boundaries capacitance circuits. The value of impedance decreases with increase in magnetic field attributing the pinning of magnetic domain walls at the grain boundary pinning
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center. This observation is further realized from the fitted parameters of Nyquist plots.
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(e) Temperature dependent dielectric constant is found to increase with increase in temperature for sufficient amount of thermal energy acquired by the charge carriers to overcome the resistive barrier.
(f) Impedance value with temperatures is found to decrease indicating temperature dependent electrical relaxation process in the system.
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(g) The estimated Ea from the Arrhenius fit, relaxation and conduction process of those nanocomposites reveals that same kind of charge carriers are governing both electrical processes
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in the system. (h) Temperatures dependent ac conductivity curves are found to be well fitted by Jonscher’s double power law. The temperature dependent conduction process is assisted by mixture of both
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small and large polaronic mechanism in the system.
Acknowledgement
One of the authors S. K. Mandal acknowledges the DST Project (No. SR/FTP/PS-
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019/2012), India for providing us some experimental facilities.
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[2]C. Israel, S. Kar-Narayan, Neil D. Mathur, IEEE Sensors Journal, 10(2010) 914 – 917.
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[10] C. A. F. Vaz, J. Hoffman, Y. Segal, M. S. J. Marshall, J. W. Reiner, Z. Zhang,R. D. Grober,
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F. J. Walker, C. H. Ahn, J. Appl. Phys. 109 (2011) 07D905 – 1 – 07D905 – 6. [11] J. B. Huarac, R. Martinez, G.Morell, J. Appl. Phys. 115 (2014) 084102 – 1 – 084102 – 7. [12] M. Kumar, S. Shankar, G. D. Dwivedi, A. Anshul, O. P. Thakur, A. K. Ghosh, Appl. Phys. Lett. 106 (2015) 072903 – 1 – 072903 – 4. [13] Z. Duan, X. Shi, Y. Cui, Y. Wan, Z. Lu, G. Zhao, J. Alloys Compd. 698 (2017) 276 – 283. [14] P. Martins, D. Silva, M. P. Silva, S. Lanceros-Mendez, Appl. Phys. Lett. 109 (2016) 112905-1 - 112905-5.
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[15] R. Brito-Pereira, C. Ribeiro, S. Lanceros-Mendez, P. Martins, Composites Part B: Engineering 120 (2017) 97–102. [16]P. Martins, M. Silva, S. Reis, N. Pereira, H. Amorín, S. Lanceros-Mendez,Polymers 9 (2017)
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Nanotechnology 28 (2017) 065707-1-065707- 9.
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[18] T. Zheng, Z. Yue, G. G. Wallace, Y. Du, P. Martins, S. Lanceros-Mendez, M. J. Higgins,
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[19] C. Thirmal, C.Nayek, P. Murugavel, V. Subramanian, AIP Advances 3 (2013) 112109 – 1 – 112109 – 8.
[20]Y. Shen, J. Gao, Y. Wang, J. Li, D. Viehland, J. Appl. Phys. 115 (2014)094102 – 1 – 094102 – 4.
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[21] F. Yan, K. Han, G. Zhao, X. Shi, N. Song, Z. Jiao, Mater. Charact. 124 (2017) 90–96. [22] S. K. Mandal, A. K. Das, T. K. Nath, D. Karmakar, B. Satpati,J. Appl. Phys.100 (2006) 104315 – 1 – 104315 – 8.
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[23] D. Karmakar, S. K. Mandal, R. M. Kadam, P. L. Paulose, A. K. Rajarajan,T. K. Nath, A. K. Das, I. Dasgupta, G. P. Das, Phys. Rev. B75 (2007) 144404 – 1 – 144404 – 14.
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[24] D. Karmakar, T. V. C. Rao, J. V. Yakhmi, A. Yaresko, V. N. Antonov, R.M. Kadam, S. K. Mandal, R. Adhikari, A. K. Das, T. K. Nath, N. Ganguli, I. Dasgupta, G. P. Das, Phys. Rev. B81 (2010) 184421 – 1 – 184421 – 13. [25] S. K. Mandal, T. K. Nath, A. Das, J. Appl. Phys.101 (2007) 123920 – 123920 – 7. [26] S. K. Mandal, A. K. Das, T. K. Nath, D. Karmakar, Appl. Phys. Lett.89 (2006) 144105 -1 144105 – 3.
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[27] S. K. Mandal, P. Dey, T. K. Nath, J. Vac. Sci. Technol. B32 (2014) 041803–1– 041803 – 8. [28] A. L. Patterson, Phys. Rev. 56 (1939) 978- 982.
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[29] G. Srinivasan, E. T. Rasmussen, A. A. Bush, K. E. Kamentsev, V. F. Meshcheryakov, Y. K. Fetisov, Appl. Phys. A 78 (2004) 721–728.
[30]J. C. Maxwell “Electricity and Magnetism” Oxford University Press, New York, 1 (1993)
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828.
[31] S. Dussan, A. Kumar, J. F. Scott, R. S. Katiyar, AIP Adv. 2 (2012) 032136 -1 – 032136 -11.
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[32]J. R. Macdonald, W. B. Johnson, Fundamentals of Impedance Spectroscopy, in Impedance Spectroscopy: Theory, Experiment, and Applications, John Wiley & Sons, Inc., Hoboken, 2005. [33] P. Dey, T. K. Nath, Phys. Rev. B 73, (2006) 214425 – 1 – 214425 – 14. [34] Y. Wang, H. Qin, S. Ren, J. Hu, Physics B 425 (2013) 17 – 22.
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[35] Z. Ž. Lazarević, Ć. Jovalekić, A. Milutinović, D. Sekulić, V. N. Ivanovski, A. Rečnik, B. Cekić, N. Ž. Romčević, J. Appl. Phys. 113 (2013) pp. 18722- 1-18722-11.
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[36] S. Saha, T. P. Sinha, Phys. Rev. B 65 (2002) 134103-134106. [37] S. K. Mandal, T. K.Nath, I. Manna, Nanoscience and Nanotechnology Letters 1 (2009) 99–
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106.
[38] S. K. Mandal, S. Singh, P. Dey , J.N. Roy, P.R. Mandal, T. K. Nath, J. Alloys Compd.656 (2016) 887-896.
[39] P. R. Das, S. Behera, R. Padhee, P. Nayak, R. N. P. Choudhary, Journal of Advanced Ceramics 1 (2012) 232-240. [40] K. Funke, Prog. Solid State Chem. 22, (1993) 111.
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[41] A. Pelaiz – Barramco, M. P. Gutierrez – Amador, A. Huanosta, R. Valenzuela, Appl. Phys. Lett., 73 (1998) 2039.
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[42] S. R. Elliott, Adv. Phys. 36 (1987) 135.
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FIGURE CAPTIONS Fig. 1 (Color online) Room temperature XRD patterns for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO – 0.9PZT nanocomposite. Analysis of XRD pattern reveals the formation of single
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phase nanoparticles.
Fig. 2 (Color online) (a) αE31 vs. H, (b) αE33 vs. H, for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites.αE vs. f for (c) 0.05LSMO – 0.95PZT and for (d) 0.1LSMO – 0.9PZT
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nanocomposites, respectively. Inset in (d) shows room temperature P – E loop at 10 Hz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites.
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Fig. 3 (Color online) ε vs. f curves at different H for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO – 0.9PZT nanocomposite, indicating Maxwell Wagner interfacial polarization at low f region. tanδ vs. f curves at different H for (c) 0.05LSMO – 0.95PZT and (d) 0.1LSMO – 0.9PZT nanocomposite, indicating loss in the sample. Inset in (a) and (b) show MD (%) vs. H curves at f
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= 1 ad 2kHz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposite, respectively. Inset in (c) and (d) show ML (%) vs. H curves at f = 1 and 2 kHz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposite, respectively.
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Fig. 4(Color online) (a) Z′ vs. f, (b) Z″ vs. f and (c) Nyquist plots at different H for 0.05LSMO – 0.95PZT nanocomposites. (d) Z′ vs. f, (e) Z″ vs. f and (f) Nyquist plots at different H for
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0.1LSMO – 0.9PZT nanocomposites. Impedance study shows grain boundary pinning center at ferromagnetic grains. Inset in (b) show parallel combination of grain boundaries resistance and grain boundaries capacitance circuit. The red solid lines show the fitting of the curves. Fig. 5(Color online) (a) Rm vs. H and (c) Zm vs. H curves at 73 and 200 Hz for 0.05LSMO – 0.95PZT nanocomposites. (b) Rm vs. H and (d) Zm vs. H curves at 73 and 200 Hz for 0.1LSMO –
24
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0.9PZT nanocomposites. Insets in (c) and (d) show Xm vs. H curves at 73 and 200 Hz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposite, respectively. Fig. 6(Color online)ε as a function of f at different temperatures for (a) 0.05LSMO – 0.95PZT
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and (b) 0.1LSMO – 0.9PZT nanocomposites. tanδ as a function of f at different temperatures for (c) 0.05LSMO – 0.95PZT and (d) 0.1LSMO – 0.9PZT nanocomposites.
Fig. 7(Color online) (a) Z′ vs. f (b) Z″ vs. f and (c) Nyquist plots at different temperatures for
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0.05LSMO – 0.95PZT nanocomposites. (d) Z′ vs. f (e) Z″ vs. f and (f) Nyquist plots at different temperatures for 0.1LSMO – 0.9PZT nanocomposites. Impedance study shows that temperature
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dependent electrical relaxation process in the systems. Inset in (a), (b) and (c) show the magnified view of Z′ vs. f, Z″ vs. f and Nyquist plots at high temperature for 0.05LSMO – 0.95PZT nanocomposites. Insets in (d), (e) and (f) show the magnified view of Z′ vs. f, Z″ vs. f and Nyquist plots at high temperature for 0.1LSMO – 0.9PZT nanocomposites. The red solid
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lines show the fitting of the curves.
Fig. 8(Color online) Normalised Z″/Z″o vs. f/fo curve at various temperatures for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO – 0.9PZT nanocomposites, Z″o is complex impedance at resonance.
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Overlapping of the curves indicates temperature independent dynamical process in the system. Fig. 9(Color online) (a) ln(τ)vs. 103/T curves for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO –
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0.9PZT nanocomposites. σdc vs. 103/T curves for (c) 0.05LSMO – 0.95PZT and (d) 0.1LSMO – 0.9PZT nanocomposites. The Ea obtained from both the curves indicates both relaxation and conductivity processes are determined by same type of charge carriers. Red solid lines show the fitted curve.
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Fig. 10(Color online) σac vs. f at different temperatures for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO – 0.9PZT nanocomposites, which shows that conductivity increases with increase in temperatures and f. Red solid lines show the fitted curve.
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Fig. 11(Color online) n and p as a function of temperatures for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO – 0.9PZT nanocomposites, which shows that conductivity determined by both small
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and large polarons hopping mechanism.
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Table I: Fitted parameters obtained from Z″ vs. f curves at different magnetic fields for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites.
500 1000
Cgb2 (nF) 7.07 (±0.01) 14.11 (±0.01) 8.00 (±0.05) 7.51 (±0.01)
Rgb1 (kΩ) 689.51 (±0.01) 674.33 (±0.01) 651.98 (±0.02) 640.72 (±0.02)
0.1LSMO – 0.9PZT Cgb1 Rgb2 (nF) (MΩ) 0.76 1.04 (±0.01) (±0.01) 0.80 1.15 (±0.01) (±0.01) 0.81 1.16 (±0.01) (±0.01) 0.84 1.29 (±0.02) (±0.01)
Cgb2 (nF) 7.76 (±0.01) 7.14 (±0.01) 6.29 (±0.03) 6.87 (±0.01)
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50
0.05LSMO – 0.95PZT Cgb1 Rgb2 (nF) (MΩ) 1.08 1.30 (±0.01) (±0.01) 1.00 1.11 (±0.01) (±0.01) 1.01 0.90 (±0.01) (±0.01) 1.03 0.93 (±0.01) (±0.01)
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0
Rgb1 (kΩ) 870.02 (±0.03) 807.63 (±0.01) 547.92 (±0.01) 530.14 (±0.01)
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H (Oe)
Table II: Fitted parameters obtained from Z″ vs. f curves at different temperatures for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites.
100 150 200
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50
0.05LSMO – 0.95PZT Cgb1 Rgb2 (nF) (MΩ) 3.69 1.54 (±0.03) (±0.02) 8.17 1.62 (±0.08) (±0.03) 16.81 0.23 (±0.02) (±0.02) 24.16 0.034 (±0.05) (±0.003) 27.30 0.008 (±0.02) (±0.001)
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RT
Rgb1 (kΩ) 120.14 (±0.05) 36.39 (±0.01) 1.68 (±0.01) 0.71 (±0.02) 0.30 (±0.04)
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T (oC)
Cgb2 (nF) 4.66 (±0.01) 23.37 (±0.01) 50.96 (±0.02) 27.14 (±0.03) 35.64 (±0.05)
27
Rgb1 (kΩ) 483.88 (±0.01) 246.48 (±0.01) 163.55 (±0.01) 4.98 (±0.01) 1.68 (±0.01)
0.1LSMO – 0.9PZT Cgb1 Rgb2 (nF) (MΩ) 1.81 0.79 (±0.01) (±0.01) 2.60 0.35 (±0.01) (±0.01) 4.31 0.056 (±0.02) (±0.002) 3.56 0.010 (±0.01) (±0.001) 3.56 0.0030 (±0.01) (±0.0002)
Cgb2 (nF) 9.46 (±0.01) 8.71 (±0.01) 5.96 (±0.03) 26.96 (±0.01) 27.07 (±0.01)
I (arb. unit) 165
110
100 *
*
55
0 20 *
*
40
Fig. 1
(220)
(211)
(120)
(a) 0.05LSMO - 0.95 PZT *PZT + LSMO
* *
U*,+S (130, 341) CR IP T
0
(020)
(110)
*
*
*
*
*
*
2 (degree) 60
*,+ (130, 341)
200
*,+ (111, 211)
(010)
300
AC *, + (111, 211)(110) C E (020) P (120) T ED (211) M AN (220)
(010)
I (arb. unit)
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(b)
0.1LSMO - 0.9PZT
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xLSMO - (1-x)PZT
x = 0.05
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(d)
2
TE D 0
H (kOe)
1
20
0 15
0.07 0.00
10
-0.07
EP δE
AC C
-1
40
H= 800 Oe
0.14 xLSMO -(1-x)PZT
P (C/cm )
E33 (mV/cm-Oe)
(b)
0.0
E33
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Hac
-0.8 0.5
-2
E31
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0.0
-0.5
(c) 60
E (mV/cmOe)
(a)
f = 10 Hz x = 0.05 x = 0.1
-0.14 -88
-44
0
E (V/cm)
H Hac
44
88
5
x = 0.1 H= 600 Oe
0 2
0
Fig. 2
5
E (mV/cmOe)
xLSMO - (1-x)PZT x= 0.05, 2 kHz x= 0.1, 1 kHz
δE
E31 (mV/cm-Oe)
0.8
10
f (kHz)
15
20
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0.05LSMO - 0.95PZT
0.05LSMO - 0.95PZT
(c)
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ML (%)
1080
0.05LSMO - 0.95PZT
4
1 kHz 2 kHz
0 Oe 300
600
H (Oe)
0.2
900
0.1
0
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MD (%)
0.1LSMO - 0.9PZT
300
600
300
600
H (Oe)
EP
4
10
5
10
6
10
0.0
0.0
0.05LSMO - 0.95PZT 1 kHz 2 kHz
-0.4
1.2
-0.8
0.8
-1.2 0
900
H (Oe)
0.1LSMO - 0.9PZT 3
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1 kHz 2 kHz
0
10
MD (%)
(d)
0.6
1500
2
1 kHz 2 kHz
1000 Oe
0.0
10
5
500 Oe
0.3
3000
0.05LSMO - 0.95PZT
0
50 Oe
900
0.3
10
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0
(b)
4500
0
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540
0 Oe 50 Oe 500 Oe 1000 Oe
0.4
15
MD (%)
8
tan
(a)
tan
1620
300
600
900
H (Oe)
0.4
0.1LSMO - 0.9PZT 2
10
3
10
4
10
f (Hz)
f (Hz)
Fig. 3
5
10
6
10
10
10
5
10
f (Hz)
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2
10
3
10
4
10
10
(d) 0.9
0.6
0.1LSMO - 0.9PZT 0.6
0.0 0.6
(b)
Rgb1
Rgb2
Cgb1
Cgb2
0.4
0.0
0.4
0.2
0.0
(f) 0.4
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EP
0.0 0.6 (c)
0.3
0.3
(e)
TE D
0.2
0 Oe 50 Oe 500 Oe 1000 Oe Fit
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0.3
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0 Oe 50 Oe 500 Oe 1000 Oe Fit
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Z'(M)
0.05LSMO - 0.95PZT
Z"(M)
6
10
(a)
0.9
Z" (M)
5
10
0.2
0.0
0.0 0.0
0.3
0.6
Z' (M)
Z' (M)
4
Z" (M)
10
f (Hz)
3
0.9 0.0
0.2
Fig. 4
0.4
0.6
Z' (M)
0.8
Z" (M)
2
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(a)
Xm (%)
73 Hz 200 Hz
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-15
-30
-16
-20
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-35
-20
900
-25
(d)
TE D
4
5 0.1LSMO - 0.9PZT
EP
73 Hz 200 Hz
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Xm (%)
7
3
4
6 5
73 Hz 200 Hz
4
0.1LSMO - 0.9PZT
300
300
600
H (Oe)
300
900
Fig. 5
600
H (Oe)
600
900
900
Zm (%)
(b)
0.1LSMO - 0.9PZT
Rm (%)
600
73 Hz 200 Hz
-24 5
300
0.05LSMO - 0.95PZT
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Rm (%)
0.05LSMO - 0.95PZT
-25
73 Hz 200 Hz
-12
-20
(c)
0.05LSMO - 0.95PZT
Zm (%)
-8
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(c)
(a)
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30
tan
3
0
(b) 0.1LSMO - 0.9PZT
(d)
TE D
0.1LSMO - 0.9PZT
9
6
EP
20
RT o 50 C o 100 C o 150 C o 200 C
AC C
10
3
0 2
10
3
10
4
10
5
10
6
10
2
10
f (Hz)
3
10
4
10
f (Hz) Fig. 6
5
10
6
10
tan
8
6
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x 103
RT o 50 C o 100 C o 150 C o 200 C
4
x 103
0.05LSMO - 0.95PZT
0.05LSMO - 0.95PZT
12
9
10
2
6
10
4
10
(a)
10
5
6
10
10
RT o 50 C 0.01 o 100 C o 150 C o 200 C Fit 0.00
RT o 50 C 0.02 o 100 C o 150 C o 200 C Fit
0.5
f (Hz)
3
10
10
0.6
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Z' (M)
1.0
10
5
0.00
2
2
10
3
4
10
10
5
10
3
10
6
10
0.05LSMO - 0.95PZT
10
4
10
0.4 10
5
10
6
(d)
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0.1LSMO - 0.9PZT
0.0 0.6
0.0 (e)
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(b) 0.01
0.2 0.00 2
10
10
3
4
10
0.0 0.6
10
5
0.3
EP Z" (k)
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0.2
0.00 2
10
3
10
4
5
10
6
10
10
0.1
6
10
10
0.0
(f)
0.4
(c)
0
0.3
0
40 80 Z' (k)
4
Rgb1
Rgb2
Cgb1
Cgb2
Z" (k)
Z" (M)
0.4
0.01
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Z" (M)
0.02
0.4
0.2
0.2
2 0 0
0.0 0.0
0.2
0.4
Z' (M)
0.6
Z" (M)
10
4
0.8 0.0
Fig. 7
0.2
0.4
Z' (M)
6
Z' (k)
12
0.6
0.0
Z" (M)
3
Z' (M)
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f (Hz) 2
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f/fo
-1
0
10
10
1
10
10
4
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0.05LSMO - 0.95PZT
150oC
0.6
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200oC
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0.3
0.0
TE D
0.9
0.1LSMO - 0.9PZT
100oC
EP
0.6
(b)
150oC 200oC
AC C
Z"/Z"o
3
10
(a)
0.9
Z"/Z" o
2
10
0.3
0.0 -2
10
-1
10
0
10
1
10
f/fo
Fig. 8
2
10
3
10
4
10
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3
3
-1
10 /T (K ) 2.2
-1
10 /T (K )
2.4
2.2
2.6
2.4
2.6
-5.6
(c)
2
Ea
Parameters
Values
2.6
3
-1
lndc (cm)
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0.31
=
1.16
0.42
4.65
0.12 Ea/k
=
-5.38
0.16
2.4
2.6
2.8
-1
-10
-12
=
0.4
6e
V
-14
Error
Values
ln() 2
R = 0.998
R = 0.998
2.4
0.1LSMO - 0.9PZT
E
Error Parameters
2
2.2
-15
V
(d)
-20.66
AC C
-10
0.4
7e
0.49
ln() = ln() + E /k T ln(dc) = ln() - Ea/k T a
ln() = E /k = a
=
0.20
-5.44
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V
EP
ln (s)
0.1LSMO - 0.9PZT
=
-1.17
a
Error
R = 0.997
(b)
e 0 4 0.
ln() = E /k = a
Values
E
-14
2
R = 0.994
-8
Parameters
Expt. Fit
-13
lndc (cm)
-6
ln(dc) = ln() - E /k T a
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-6.4 0.05LSMO - 0.95PZT Expt. Fit ln() = ln() + E /k T -7.2 a V Error Parameters e Values .40 0 1.02 ln() = -18.25 = a E -8.0 0.43 E /k = 4.69 a
0.05LSMO - 0.95PZT
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ln (s)
(a)
3.0
2.2
-1
-16 3
2.8
-1
10 /T (K )
10 /T (K )
Fig. 9
3.0
1E-4
0.1 0.01
1E-5
0.05LSMO - 0.95PZT (b)
5
10
TE D
AC C
EP
ac(cm)
0.01
1E-3
3
10
o
200 C
0.1LSMO - 0.9PZT
-1
0.1
II
I
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1E-3
1E-6
0.05LSMO - 0.95PZT III
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ac(cm)
-1
0.01
(a)
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1E-3
RT ACCEPTED MANUSCRIPT o 50 C o 100 C o 150 C o 200 C Fit
0.1
1E-4 1E-5
2
10
3
10
4
10
f (Hz) Fig. 10
5
10
6
10
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(c) 0.63 0.1LSMO - 0.9PZT
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(a)
SC
n
0.57
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0.6
(d)
TE D
0.5 (b) 2.0
1.99
EP
1.8
1.6 50
AC C
1.7
100
o
0.54 2.00
p
1.9
p
0.60
n
0.05LSMO - 0.95PZT
0.7
1.98
1.97 150
200
50
T ( C)
100
o
150
T ( C)
Fig. 11
200
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Highlights #Magnetoelectric response has been detected in these multiferroic nanocomposites at room.
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#Dielectric constant reveals Maxwell Wagner interfacial polarization at low frequency regime.
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#Field dependent impedance attributes depinning of domain walls at the grain boundaries.
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# Estimated activation energy indicates the same type of charge carrier for both the process.
#Conductivity follow Jonscher’s double power law attributes small and large polaronic
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EP
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hopping.
S0925-8388(17)31876-5
DOI:
10.1016/j.jallcom.2017.05.259
Reference:
JALCOM 41990
To appear in:
Journal of Alloys and Compounds
Received Date: 5 March 2017 Revised Date:
6 May 2017
Accepted Date: 25 May 2017
Please cite this article as: S.K. Mandal, S. Singh, R. Debnath, A. Nath, P. Dey, Magnetoelectric coupling, dielectric and electrical properties of xLa0.7Sr0.3MnO3 – (1−x) Pb (Zr0.58Ti0.42)O3 (x = 0.05 and 0.1) multiferroic nanocomposites, Journal of Alloys and Compounds (2017), doi: 10.1016/ j.jallcom.2017.05.259. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Magnetoelectric Coupling, Dielectric and Electrical Properties of xLa0.7Sr0.3MnO3 – (1-x) Pb (Zr0.58Ti0.42)O3 (x = 0.05 and 0.1) Multiferroic Nanocomposites
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S. K. Mandal*, Swati Singh, Rajesh Debnath and A. Nath Department of Physics, National Institute of Technology Agartala, Agartala, Tripura, 799046, India P. Dey
Abstract
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Department of Physics, Kazi Nazrul University, Asansol, 713304,W.B., India
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We have investigated magnetoelectric coupling, dielectric and electrical properties of xLa0.7Sr0.3MnO3(LSMO)– (1-x) Pb(Zr0.58Ti0.42)O3 (x = 0.05 and 0.1) nanocomposites, prepared through low temperature pyrophoric reaction process. Magnetoelectric response has been detected in these multiferroic nanocomposites at room temperature attributing the presence of magnetostriction properties of piezomagnetic material. Noticeably, all nanocomposites are found to exhibit room temperature ferroelectric behavior. Studies of dielectric constant of those
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nanocomposites reveal the Maxwell Wagner interfacial polarization at low frequency regime. The ac electrical properties of nanocomposites have been studied employing impedance spectroscopy technique. The value of impedance has been found to decrease with increase in
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magnetic field attributing to the depinning of LSMO domain walls at the grain boundaries pinning centres and thereby enhancing the spin dependent transport mechanism in the composites. Impedance study at different temperatures shows temperature dependent electrical
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relaxation process in the system. The activation energy is estimated from Nyquist plots, dc and ac conductivity data using the Arrhenius relation. This is indicating that the same type of charge carrier is responsible for both the relaxation and the conduction processes in the system. Ac conductivity curves follow a Jonscher’s double power law. The conduction mechanism in temperature is mainly due to the small and large polaronic hopping in the system.
Key words: Magnetoelectric coupling, Multiferroic, Nanocomposites. *
Corresponding author: Tel: +913812348530 E-mail address:[email protected] (S. K. Mandal) 1
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I. INTRODUCTION Magnetoelectric (ME) coupling is a process of combining spontaneous magnetization and
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ferroelectric polarization simultaneously in a single system. ME materials have fascinated many researchers for their ability to perform different functions simultaneously. They are promising candidates for potential use in memory based devices, such as in spintronics and magnetic field sensors applications. In ME materials, the induced polarization (P) is directly proportional to the
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applied dc magnetic field (H) as P = αH, where α is the second rank ME-susceptibility tensor.
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The term α is determined by measuring δP in an applied ac magnetic field (δH). ME voltage coefficient, αE = δE/δH is directly related to α by an expression as α = εoεrαE, where εo and εr is the free space permittivity and relative permittivity of the material, respectively [1]. There is very less material available in nature, such as BiFe2O3, which exhibits ME effect in single phase. However, the effect is restricted at very low temperature and hence such material is not
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promising for commercial applications. This fact has motivated many researchers to initiate synthesis and study of multiferroic composites, films and multilayers in order to obtain enhanced ME effect at room temperature. Multiferroic nanocomposites, exhibiting ME effect have
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triggered intense research interest from past few years due to its probable applications in
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magnetic field sensors [2], multiple – state memories [3], data – storage devices [4] etc. In composite systems, ME effect is an extrinsic property [5], which derives from ME
coupling between the magnetic and piezoelectric phases. Thus, in order to achieve a relatively strong ME signal from multiferroic ME composites, the two basic requirements are : (1) a high piezoelectric material and (2) a strong magnetic material [6, 7]. Outstanding piezoelectricity of Lead zirconate titanate (PZT) and excellent magnetostriction of lanthanum strontium manganese oxide (LSMO) [8] make them appealing as good candidates for ferroelectric and ferromagnetic 2
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phases, respectively, in such multiferroic composites where we can expect strong ME effect at room temperature. Z.
H.
Tang
et
al.
have
reported
enhanced
ME
response
for
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La0.67Sr0.33MnO3/PbZr0.52Ti0.48O3 bilayer thin film at room temperature, prepared through pulsed laser deposition method [9]. C. A. F. Vaz et al. have shown ME response of Pb(Zr0.2Ti0.8)O3/La0.8Sr0.2MnO3 multiferroic heterostructures [10]. J. B. Huarac et al. have
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studied ME response and magneto-dielectric properties of Ba0.7Sr0.3TiO3/La0.67Sr0.33MnO3 bifunctional nanocomposites, prepared through high temperature solid state reaction technique
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[11]. M. Kumar et al. have reported large magnetoresistance of La0.67Sr0.33MnO3-BaTiO3 nanocomposite, prepared through sol – gel method [12]. Z. Duan et al. have shown ME response of layered composite film of Pb(Zr0.52Ti0.48)O3/La0.67Sr0.33MnO3, prepared through a chemical solution deposition method [13]. P. Martins et al. have investigated magneto-dielectric effect of
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series of xCoFe2O4/(1-x)PVDF nanocomposites, where x = 20% sample shows highest magnetodielectric effect [14]. R. Brito-Pereira et al. have shown ME response increasing with increase in Terfenol –D, contained in Terfenol –D/P(VDF-TrFE) composite [15]. P. Martins et al. have
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reported maximum ME response for 30 wt% of Terfenol-D in Terfenol-D/CoFe2O4/P(VDFTrFE) composite, prepared through solvent casting technique [16]. N. Adhlakha et al. have
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studied structural, dielectric, magnetic and ME effect of (1-x)(0.3CoFe2O4-0.7BiFeO3)-xPVDF nanocomposites film, prepared through hot press method, where they have shown maximum ME response for x = 0.4 samples [17]. T. Zheng et al. have shown piezoelectric response of PVDF/Fe3O4 composite nanofibers and confirms a nanoscale ME effect using Piezoresponse Force Microscopy technique [18]. Ch. Thirmal et al. have investigated magneto-dielectric response of PVDF - La0.7Sr0.3MnO3 polymer nanocomposite thick film, fabricated by dip coating
3
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technique [19]. High ME coupling effect have been reported for Metglas/PMN-PT laminate composites [20]. F. Yan et al. have investigated ME coupling in C-axis oriented
[21]. In
our
study,
we
have reported
ME
effect
in
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La0.67Sr0.33MnO3/PbZr0.52Ti0.48O3 films, fabricated by sol-gel method on LaAlO3 (00l) substrates
xLa0.7Sr0.3MnO3(LSMO)
–
(1-x)Pb(Zr0.58Ti0.42)O3 (PZT) (x = 0.05 and 0.1) perovskite multiferroic nanocomposites at room
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temperature. ME coefficient (αE) as a function of dc magnetic field has been studied for 0.1LSMO – 0.9PZT composite at a frequency of 1kHz and for 0.05LSMO – 0.95PZT composite
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at 2 kHz in both transverse and longitudinal configurations. Moreover, magneto-dielectric studies give evidence of ME effect in all those composites. Dielectric study of those nanocomposites gives the evidence of Maxwell Wagner interfacial polarisation at low frequency region at different applied magnetic field. Furthermore, we have carried out complex impedance
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properties of nanocomposites at room temperature with varying magnetic field. Nyquist plots are fitted using parallel combinations of resistance – capacitance circuit showing dominant effect of grain boundary pinning centre in the system. Apart from the magnetic field dependence, the
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effects of temperatures on dielectric and electrical properties have also been investigated. Nyquist plots reveal temperature dependent electrical relaxation process in the system.
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Furthermore, the activation energy is estimated from relaxation time, dc conductivity and ac conductivity of those nanocomposites. II. EXPERIMENTAL DETAILS Multiferroic nanocomposites xLSMO – (1-x)PZT (x = 0.05 and 0.1) have been prepared by low temperature chemical “pyrophoric reaction process”[22 -27] and solid state route. The LSMO phase were prepared from high-purity La2O3 (Alfa Aesar, 99.99%), Sr(NO3)2(Merck, 4
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99.0%) and Mn(CH3COO)2 (Merck, 99.0%). The required amount of La2O3, Sr(NO3)2.9H2O, Mn(CH3COO)2 and Ho(NO3)2 were mixed in a distilled water. All the nitrates and acetate were soluble in distilled water. Then the solution is heated at ~180̊C for few minutes with continuous
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stirring. After some time, TEA was added in the solution with metal ions maintaining the ratio 4:1:1 (TEA :La,Sr: Mn). After adding TEA, the solution became viscous and colloidal. The metal ions were precipitated in the solution. At the same temperature, HNO3 was added to
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dissolve the precipitation and then the clear solution was evaporated with constant stirring. After complete dehydration, the nitrate themselves were decomposed with the evolution of brown
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fumes of NO2 leaving behind a voluminous, organic based, brownish black, fluffy powder known as precursor powder. The precursor powder was mechanically grinded, and then calcined at temperatures of 800 ̊C in air for 5 hours to get nanocrystalline powders. The chemical reaction
Mn+ + N(CH2CH2OH)3 (Metal ion = La,Sr, Mn)
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involved in the preparation of LSMO nanopowder is as follows:
(Metal ion – TEA complex)
M2On+ CO2+H2O
1800C
O + + H2O
M – H2C O
Calcination
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+ Co2 +NO2 + C
[M – N(CH2CH2OH)3]n+
(n-1)+
(Nano sized composite powder)
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After preparation of LSMO nanoparticles, we have mixed it with requisite amount of PZT powder (purchased from APC International Ltd. USA) for 10 hrs. Then the mixed powder has been again calcined in air for 5 h at a temperature of 8000 C to obtain the required nanometric composite phase. We have made circular pellets from calcined nano powders and have sintered them for 30 minutes. The sintering temperatures were same as that of calcination temperatures for all those nanocomposites. Then these pellets have been used for electrical measurements. We
5
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have done electrode on the sample surface using high temperature silver paste and have used two probes measurement technique. For ME measurement we have poled the electrode samples. After poling we have used 42 gauge copper wire as an electrical leads.
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Structural characterization has been done by X-ray diffraction technique (XRD) (Bruker D8 Advanced) with monochromatic Cu-Kα radiation. For ME measurement, we have used ME measurement setup comprising of electromagnet (Polytronic laboratory electromagnet, EM –
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100), electromagnet power supply (Polytronic power supply – CCP – 100Y), wide band power amplifier (Krohn – Hite corporation– 7500), lock – in amplifier (Stanford research system –
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SR830), Helmholtz coil, function generator and Keithley multimeter. The ME measurements have been carried out for two different field orientations: (1) transverse configuration where H and Hac are parallel and δE perpendicular to the sample plane. The ME coefficient in transverse configuration is represented by αE31 and (2) longitudinal configuration where H, δH and δE are
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perpendicular to the sample plane. The ME coefficient in longitudinal configuration is represented by αE33. The two configurations are shown in inset of Figs. 2 (a) and (b). The electrical characterizations have been carried out in LCR meter (HIOKI -3532-50 LCR
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HiTESTER) at different magnetic field. For electrical measurement, the magnetic field has been applied using an electromagnet (Nuis Technologies). Polarization-electric field measurements
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have done employing Sawyer –Tower circuit using mixed domain oscilloscope (Tektronix, MDO-3054).
III. RESULTS AND DISCUSSION A. RESULTS (a) Structural Characterization
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Structural characterization has been done through XRD technique at room temperature. The detailed study of XRD patterns of 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 1 (a) and (b), respectively. The average crystallite size (Φ)for
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0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZTnaocomposites has been calculated through XRD patterns using Scherrer formula as [28]: Φ= kλ/βeffcosθ
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where, Φ is the average diameter of the nanocrystals in Å, k is the shape factor, λ is the wavelength of CuKα radiation (1.542Å), θ the diffraction angle and βeff defined as
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βeff2= βm2-βs2
where,βm and βs are the experimental full width half maxima of the present sample and that of a standard silicon sample, respectively. The standard silicon sample is used to calibrate the intrinsic width associated with the equipment. The average crystallite size is found to (Φ ~ 41 nm
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±1 %) for LSMO phase, and (Φ ~ 31 nm ±1 %) for PZT phase for 0.05LSMO-0.95PZT nanocomposites, and (Φ ~ 42 nm ±1 %) for LSMO phase and (Φ ~ 29 nm ±1 %) for PZT phase for 0.1LSMO-0.9PZT nanocomposite. We have indexed the XRD peaks using JCPDS software
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and data sheet 49- 0595and 73 – 2022 for LSMO and PZT nanoparticles, respectively.
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(b) Magnetoelectric Coupling
αE as a function of H has been measured by swiping dc magnetic field from +H to -H and
-H to +H for all the nanocomposites. αE as a function of H at a frequency(f) of 2 kHz and 1 kHz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 2 (a) and (b), respectively. For x = 0.1 sample, during positive cycles αE31 gradually increases with H showing a peak at ~ 600 Oe, followed by a gradual decrease with further increase in H. During negative cycles of H, similar behavior has been observed but in negative direction. Similar 7
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behavior has also been observed for x = 0.05 sample but peak has been observed at a H of ~800 Oe, as shown in Fig. 2 (a).The value of αE31 is found to be ~ 0.95 mV/cmOe a ta H of ~ 600 Oefor 0.1LSMO – 0.9PZT and ~0.52 mV/cmOe at a H of ~ 850 Oe for 0.05LSMO – 0.95PZT
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nanocomposites. We have also measured αE33 as a function of H at a f of 2 and 1kHz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites, as shown in Fig. 2(b).Similar behaviors are found in αE33 vs. H curves for both the nanocomposites. The value ofαE33is found to
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~ 0.54 mV/cmOe at H of ~ 760 Oe for 0.1LSMO – 0.9PZTnanocomposite and ~ 0.36 mV/cmOe at H of ~ 970 Oe for 0.05LSMO – 0.95PZT nanocomposite. αE as a function of f has been carried
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out for 0.05LSMO – 0.95PZTnanocompositeat a H of ~ 800 Oe and for 0.1LSMO – 0.9PZT nanocomposites at a H of ~ 600 Oe, as shown in Fig. 2 (c) and 2 (d), respectively. αE shows a sharp peak at a f ~1kHz for 0.1LSMO – 0.9PZT and ~2 kHz for 0.05LSMO – 0.95PZT nanocomposites. For both the configurations, the observed variation of αE with H may be due to
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the variation of piezomagnetic coefficient with H of piezomagnetic material of the samples [29]. In presence of ac and dc magnetic field, a dynamic strain is produced in magnetic phase. This induced strain generates an electric field in piezoelectric phase giving rise to a ME effect in the
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sample [29].The magnitude difference in transverse and longitudinal magnetoelectric coefficient may be due to the directional dependence of the magnetostriction and piezomagnetic coefficients
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[1].Furthermore, room temperature polarization vs. electric field (P – E) loops for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites at a f of 10 Hz are shown in inset of Fig. 2 (d). This measurements show the room temperature ferroelectric behavior of nanocomposites. (c) Effect of Magnetic Field on Dielectric Study Dielectric constant (ε) as a function of f at different H for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites has been investigated, as shown in Figs. 3 (a) and (b), 8
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respectively.ε is found to decrease with increase in H and f for both nanocomposites. At high f region, ε curves at different H merge and behave as independent of f. Obtained ε at an absence of H for 0.1LSMO – 0.9PZT nanocomposite is found to be ~ 3 times greater than 0.05LSMO –
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0.95PZT nanocomposite at same f. In other words, ε increases with increase in LSMO content in the composites. Although, the decrease in ε on application of H for 0.1LSMO – 0.9PZT is quiet
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less as compared to 0.05LSMO – 0.95PZT nanocomposite. The high value of ε at low f region for all H is may be explained through the light of Maxwell Wagner interfacial polarization [30].
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Simultaneously, dielectric loss [tanδ] has been studied as a function of f for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites as shown in Figs. 3 (c) and (d), respectively. It is found that tan δ decreases with increase in H for both the nanocomposites. However, the change in tanδ value with respect to H is very less throughout the measured f range for
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0.01LSMO – 0.95PZT nanocomposites. For both the nanocomposites the value of tanδ is found to < 1.6.
Apart from dielectric measurements the observed ME effect is further verified by
(%) =
() () ()
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magnetodielectric (MD) study with H and f for those nanocomposites using the relation as MD × 100, where ε(Η) is dielectric constant in presence of H and ε(0) is the
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dielectric constant in the absence of H. The MD (%) as a function of H at a f of 1 and 2kHz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocompositesare shown in inset of Figs. 3 (a) and (b), respectively. The observed MD (%) for 0.05LSMO – 0.95PZT nanocomposites is found to ~ 10 times of 0.1LSMO – 0.9PZT nanocomposites. The observed positive MD (%) is may be due to decrease in grain boundaries resistance (Rgb) of the sample. The impedance (Z) is related to Rgb as [31,32]
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Z=
+
+
where, Rg is grain resistance, Rgb is grain boundaries resistance, Rele is electrode resistance, Cg is
sample. If we consider Cgb is very small as compared to Rgb then Z α Rgb
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grain capacitance, Cgb is grain boundaries capacitance and Cele is electrode capacitance of the
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In impedance study it is found that Rgb decreases with increase in H, which supports our
relation as ML (%) =
() () ()
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experimental observations. Simultaneously, magnetolosses (ML) have been estimated using the × 100, where, tanδ (Η) is dielectric loss in presence of H
and tanδ (0) is the dielectric loss in absence of H. The ML (%) vs. f curves for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in inset of Figs. 3 (c) and (d),
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respectively. The value of ML is found to increase with increase in H for 0.05LSMO – 0.95PZT nanocomposites; while it decreases with H for 0.1LSMO – 0.9PZT nanocomposites. This is due to the grain boundaries pinning center of ferromagnetic LSMO grains [33].
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(d) Effect of Magnetic Field on Impedance Spectroscopy The measured ME coupling of those nanocomposites is f dependent. Moreover, ac
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electrical properties give the f dependence of Rgb, Cgb, Rg and Cg of the nanocomposites. Thus, real and imaginary part of impedance for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are carried out at different Hs and temperatures. Temperature dependent impedance measurement is discussed later. Real part of impedance (Zˊ) as a function of f at different Hs for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites is shown in Figs. 4 (a) and (d), respectively. Zˊvs. f curves are found to gradually decrease with increase in f
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and become constant at higher f region for both the nanocomposites. Imaginary part of impedance (Z") as a function of f at varying H for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites is shown in Figs. 4 (b) and (e), respectively. Z′ vs. f curves are found to
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gradually decrease with increase in f at different applied H for both the samples. Similar behavior is observed for Z" vs. f curves for 0.05LSMO – 0.95PZT nanocomposites whereas a small change is observed with increase in H for 0.1LSMO – 0.9PZT nanocomposites. The decreased in
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impedance (Zˊ and Z") for 0.05LSMO – 0.95PZT nanocomposites is may be due to grain boundaries pinning center of ferromagnetic LSMO grains [33]. In case of ferromagnetic grains
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the domain walls get pinned at the pinning center of the ferromagnetic grains. When H is applied, depinning of LSMO grain from grain boundaries pinning center takes place due to which electronic scattering at the conduction band get enhanced. However, in case of 0.1LSMO – 0.9PZT nanocomposites the effect of both pinning and scattering process is may be same,
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which is corroborating the small change with H. Nyquist plots at varying H for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 4 (c) and (f), respectively. Nyquist plots have been fitted using parallel combinations of grain boundaries resistance (Rgb)
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and grain boundaries capacitance(Cgb) circuits as shown in inset of Fig. 4 (b).For both the nanocomposites two such parallel combinations of Rgb and Cgb circuits have been used; first Rgb1
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and Cgb1 circuit correspond to grain boundaries resistance and grain boundaries capacitance for LSMO grains and; second Rgb2 and Cgb2 circuit correspond to grain boundaries resistance and grain boundaries capacitance for PZT grains. The fitted parameters for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Table I. A significant decrease in Rgb1 and Rgb2 with increase in H is observed for both the nanocomposites. The value of Nyquist plots is found to decrease with increase in H for 0.05LSMO – 0.95PZT nanocomposites, which indicates
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that resistivity decreases with increase in H, whereas for 0.1LSMO – 0.9PZT nanocomposites the value of Nyquist plots is found to almost independent of H. The red solid lines in Figs. 4 show the fitting of the curves.
=
() () ()
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Furthermore, ac magnetoresistance (Rm) has been estimated using the relation as Rm (%) × 100, where R(Η) is ac resistance in presence of H and R(0) is the ac resistance in
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absence of H [34]. Rm as a function of H for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Fig. 5 (a) and (b), respectively. The value of Rm increases with
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increase in H and decreases with increase in f for 0.05LSMO – 0.95PZT nanocomposites. The maximum value of |Rm (%)| is found to ~ 25 % for 0.05LSMO – 0.95PZT nanocomposites and ~ 5 % for 0.1LSMO – 0.9PZT nanocomposites at a f of 73 Hz. Similarly, we have also estimated ac magnetoimpedance (Zm) using the relation as Zm (%) =
() () ()
× 100, where Z(Η) is an ac
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impedance in presence of H and Z(0) is an ac impedance in absence of H [34]. The Zm vs. H curves for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 5 (c) and (d), respectively. For both the nanocomposites, the value of |Zm (%)|increases with
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increase in Hand is found to maximum at af of 73 Hz. Also, we have calculated an ac magnetoreactance using the relation as Xm (%) =
() () ()
× 100, where X(Η) is an ac
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reactance in presence of H and X(0) is an ac reactance in absence of H [29]. Xm vs. H curves for0.05LSMO– 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites at different fs are shown in insets of Figs. 5 (c) and (d), respectively. For both the nanocomposites the value of Xm(%) increases with increase in H. The observed Rm, Zm and Xm are attributed to the change of permeability of the materials induced by the applied H. (e) Effect of Temperature on Dielectric Study
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ε as a function off at different temperatures for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 6 (a) and (b), respectively. ε increases with increase in temperatures for both the nanocomposites and the maximum value of ε at low f region is well
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explained through the light of Maxwell Wagner model[35]. According to this theory dielectric materials are formed by combinations of two layers; first layer is conducting in nature called as grain and second layer is non-conducting called as grain boundaries[35]. We believe that when
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temperatures is increased in the system. The conducting grains acquires sufficient amount of thermal energy in order to enhance the flow of charge carriers through the grain boundaries.
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Simultaneously, tan δ has been carried out for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites as shown in Fig. 6 (c) and (d), respectively. Similarly, tanδ also increases with increase in temperatures.
(f) Effect of Temperature on Impedance Spectroscopy
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Z′ as a function of f at different temperatures for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 7 (a) and (d), respectively. Insets in Fig. 7 (a) and (d) show the magnified view of Z′ vs. f curves at high temperature for 0.05LSMO – 0.95PZT and
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0.1LSMO – 0.9PZT nanocomposites, respectively. It has been observed that for both the nanocomposites the value of Z′ decreases with increase in temperatures. Furthermore, Z″ vs. f
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curves for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 7 (b) and (e), respectively. A sharp resonance peak is observed at high temperature region for both the nanocomposites. Moreover, it is observed that the value of Z′ and Z″ decreases with increase in LSMO content in the composites, which attributes more metallic nature in the composite. Nyquist plots for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Figs. 7 (c) and (f), respectively .Furthermore, Nyquist plots have been fitted using same circuit as
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shown in inset of Fig. 4 (b). Fitted parameters for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are shown in Table II. Rgb1 and Rgb2 are found to decrease with increase in temperatures for both the nanocomposites attributing enhanced flow of charge carriers through
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the grain boundaries of the nanocomposites. The normalized Z″/Z″o spectrum with f/fo are found to almost independent of temperatures as shown in Fig. 8, which indicates no temperature dependent broadening of the spectra, where, Z″o is impedance at resonance frequency and fo is
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the resonance frequency. The overlapping of curves at all the temperatures in a single curve further confirms a temperature independent dynamical process [36].As the magnitude of Z′ and
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Z″ for both the nanocomposites is found to decrease with increase in temperature having no peak broadening indicating temperature dependent Arrhenius type in the system. The activation energy is associated with the relaxation process, which is determined by the relation as [37,38]: 2πfoτ = 1
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where, τ is relaxation time. ln (τ) vs.103/T plots for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocmposites are shown in Figs. 9 (a) and (b), respectively. ln(τ) vs.103/T plots exhibit linear behavior, whereτ is found to decrease with increase in temperatures. This in turn, indicates
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temperature – dependent electrical relaxation process in the samples. τ is found to follow
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Arrhenius nature as [31, 37, 38]:
τ = τ exp O
!"
where, τ is the pre-factor, Ea is the activation energy for relaxation process and kβ is the O
Boltzmann constant and T is the absolute temperature. The estimated value of Ea for both the nanocomposites is found to be ~ 0.40(± 0.03) eV. The value of Ea is found to similar with the reported value of LSMO – PZT super lattice structure [31]. Moreover, the value of Ea has been
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further verified from dc conductivity (σdc) data. Some steps have been followed for such fitting. σdc has been calculated using the relation as [37 - 39]:
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σdc = t/RA where, t is the thickness of the sample, R is the bulk resistance and A is the area of the sample. In order to calculate R following relation has been used as [32, 34]: 2πfoRC = 1
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where, C is the capacitance of the sample at fo. ln (σdc) vs.103/T plots for 0.05LSMO – 0.95PZT
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and 0.1LSMO – 0.9PZT nanocmposites are shown in Fig. 9 (c) and (d), respectively. Both the curves exhibit linear behavior, where ln (σdc) is increasing with an increase in temperatures. Thus, conductivity process in the system increases with increase in temperatures, which indicates negative temperature coefficient of the resistance (NTCR) of the samples [38, 39]. σdc is found to follow the Arrhenius nature by the following relation as [36 - 38]:
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σdc = σoexp
!"
where, σo is the pre exponential factor and a characteristics of the material. The estimated value
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of Ea is found to similar with the obtained value from the relaxation process. This in turn, indicates that the same kind charge carriers are responsible for both relaxation and conduction
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process in the nanocomposites systems [38, 39]. (g) AC Conductivity
The f dependent ac conductivity (σac) at different temperatures for 0.05LSMO – 0.95PZT
and 0.1LSMO – 0.9PZT nanocmpositesis shown in Figs. 10 (a) and (b), respectively. The value of σac is calculated from dielectric data of respective samples using the relation as [31, 37 - 39]: σac = ωεοεtanδ
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where, ω is the angular f, εο is the vacuum dielectric constant. At low temperatures, the σac increases with increase in f for both the nanocomposites. As we know that the grain boundaries of dielectric material are formed from oxygen ions, which mean that each grain possesses
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oxygen rich layer on the surface of grain boundary. Such grains boundaries are active at low f region, which gives the less amount of flow of charge carriers through this boundaries. As we have increased the applied field the conducting grains become more active by promoting the
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flow of charge carriers through the grain boundaries[35]. However, at high temperature, the σac
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is found to independent off at low f region. Furthermore,σacvs. f curves show three different segments for 0.05LSMO – 0.95PZT nanocomposite at high temperature as shown in inset of Fig. 9 (a) [31]. Such observation is not observed for 0.1LSMO – 0.9PZT nanocmposites. These curves have been fitted using Jonscher’s double power law as[31]: σac = σdc + Aωn + Bωp
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where, the first term σdc corresponds to f independent region (segment I), which gives the dc conductivity of the system, the second term Aωn(segment II) where 0 < n < 1 signifies low f regime, which corresponds to short range translational hopping motion and the third term Bωp
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(segment III) where 1 < p < 2 signifies high f regime, which corresponds to localized or
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reorientation hopping motion. The n and p values obtained from the fitting data are shown in Figs. 11 (a) and (b) for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocmposites, respectively. For 0.05LSMO – 0.95PZT nanocomposites the value of n exhibits continuous decrease with increase in temperature whereas the value of p continuously increases with increase in temperatures. However, both the values of n and p are decreased with increase in temperatures for 0.1LSMO – 0.9PZT nanocomposites. Moreover, some literatures[40 – 42] have discussed the dependency of n and p on temperatures and f, where an increase in f the 16
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independent parameters (n and p) are raised with temperatures corresponding to small polaronic hopping, whereas as decreased in n and p is marked by large polaronic hopping. In the present scenario, for 0.05LSMO – 0.95PZT nanocomposites the conduction in segment II is determined
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by large polarons whereas in segment III is assisted by small polarons type hopping mechanism. Similarly, the conduction process is determined by large polarons hopping mechanism for 0.1LSMO – 0.9PZT nanocomposites.
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B. DISCUSSION
Study of room temperature ME coupling of those nanocomposites at different fs gives the
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evidence of magnetostriction properties in the samples. Also, these nanocomposites are found to exhibit room temperature ferroelectric behavior. The presence of such ME coupling is further supported by room temperature magnetodielectric study of all those nanocomposites. Furthermore, dielectric study at low f region shows the evidence of Maxwell Wagner interfacial
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polarization in presence of magnetic fields. Impedance study of those nanocomposites gives the evidence of grain boundary pinning center of the ferromagnetic LSMO grains. The observed ac magneto – resistance, impedance and reactance of both the nanocomposites are originated from
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change of permeability induced by applied H. Temperatures dependent dielectric properties of those nanocomposites give the evidence of Maxwell Wagner interfacial polarization.
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Temperatures dependent impedance study shows thermally assisted relaxation process in the system. Activation energy is estimated from both temperatures dependent τ and σdc, which indicates that same kinds of charge carriers are governing both the processes. σac as a function of f at different temperatures is found to obey double power law, which is attributed that different types of charge species are responsible for conduction process. IV. CONCLUSIONS 17
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In conclusions, xLSMO – (1-x)PZT (x = 0.05 and 0.1) nanocomposites have been prepared by a low temperature chemical pyrophoric reaction process and solid state route. (a) Detailed analysis of XRD patterns shows the simultaneous existences of both LSMO and
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PZT phases in the sample.
(b) The value of αE is found to ~ 0.95 mV/cmOe for 0.1LSMO – 0.9PZTnanocomposites at H of
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~600 Oe at a f of 1kHz in transverse configuration at room temperature. The observed ME effect may be due to the magnetostriction property of piezomagnetic material.
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(c) Analysis of P – E loop shows that 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites are ferroelectric in nature at room temperature.
(d) Magnetodielectric study of those nanocomposites further confirms the existence of magnetocoupling effect in the sample.
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(d)Nyquist plots have been fitted using parallel combinations of grain boundaries resistance and grain boundaries capacitance circuits. The value of impedance decreases with increase in magnetic field attributing the pinning of magnetic domain walls at the grain boundary pinning
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center. This observation is further realized from the fitted parameters of Nyquist plots.
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(e) Temperature dependent dielectric constant is found to increase with increase in temperature for sufficient amount of thermal energy acquired by the charge carriers to overcome the resistive barrier.
(f) Impedance value with temperatures is found to decrease indicating temperature dependent electrical relaxation process in the system.
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(g) The estimated Ea from the Arrhenius fit, relaxation and conduction process of those nanocomposites reveals that same kind of charge carriers are governing both electrical processes
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in the system. (h) Temperatures dependent ac conductivity curves are found to be well fitted by Jonscher’s double power law. The temperature dependent conduction process is assisted by mixture of both
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small and large polaronic mechanism in the system.
Acknowledgement
One of the authors S. K. Mandal acknowledges the DST Project (No. SR/FTP/PS-
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019/2012), India for providing us some experimental facilities.
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FIGURE CAPTIONS Fig. 1 (Color online) Room temperature XRD patterns for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO – 0.9PZT nanocomposite. Analysis of XRD pattern reveals the formation of single
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phase nanoparticles.
Fig. 2 (Color online) (a) αE31 vs. H, (b) αE33 vs. H, for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites.αE vs. f for (c) 0.05LSMO – 0.95PZT and for (d) 0.1LSMO – 0.9PZT
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nanocomposites, respectively. Inset in (d) shows room temperature P – E loop at 10 Hz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites.
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Fig. 3 (Color online) ε vs. f curves at different H for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO – 0.9PZT nanocomposite, indicating Maxwell Wagner interfacial polarization at low f region. tanδ vs. f curves at different H for (c) 0.05LSMO – 0.95PZT and (d) 0.1LSMO – 0.9PZT nanocomposite, indicating loss in the sample. Inset in (a) and (b) show MD (%) vs. H curves at f
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= 1 ad 2kHz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposite, respectively. Inset in (c) and (d) show ML (%) vs. H curves at f = 1 and 2 kHz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposite, respectively.
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Fig. 4(Color online) (a) Z′ vs. f, (b) Z″ vs. f and (c) Nyquist plots at different H for 0.05LSMO – 0.95PZT nanocomposites. (d) Z′ vs. f, (e) Z″ vs. f and (f) Nyquist plots at different H for
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0.1LSMO – 0.9PZT nanocomposites. Impedance study shows grain boundary pinning center at ferromagnetic grains. Inset in (b) show parallel combination of grain boundaries resistance and grain boundaries capacitance circuit. The red solid lines show the fitting of the curves. Fig. 5(Color online) (a) Rm vs. H and (c) Zm vs. H curves at 73 and 200 Hz for 0.05LSMO – 0.95PZT nanocomposites. (b) Rm vs. H and (d) Zm vs. H curves at 73 and 200 Hz for 0.1LSMO –
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0.9PZT nanocomposites. Insets in (c) and (d) show Xm vs. H curves at 73 and 200 Hz for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposite, respectively. Fig. 6(Color online)ε as a function of f at different temperatures for (a) 0.05LSMO – 0.95PZT
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and (b) 0.1LSMO – 0.9PZT nanocomposites. tanδ as a function of f at different temperatures for (c) 0.05LSMO – 0.95PZT and (d) 0.1LSMO – 0.9PZT nanocomposites.
Fig. 7(Color online) (a) Z′ vs. f (b) Z″ vs. f and (c) Nyquist plots at different temperatures for
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0.05LSMO – 0.95PZT nanocomposites. (d) Z′ vs. f (e) Z″ vs. f and (f) Nyquist plots at different temperatures for 0.1LSMO – 0.9PZT nanocomposites. Impedance study shows that temperature
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dependent electrical relaxation process in the systems. Inset in (a), (b) and (c) show the magnified view of Z′ vs. f, Z″ vs. f and Nyquist plots at high temperature for 0.05LSMO – 0.95PZT nanocomposites. Insets in (d), (e) and (f) show the magnified view of Z′ vs. f, Z″ vs. f and Nyquist plots at high temperature for 0.1LSMO – 0.9PZT nanocomposites. The red solid
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lines show the fitting of the curves.
Fig. 8(Color online) Normalised Z″/Z″o vs. f/fo curve at various temperatures for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO – 0.9PZT nanocomposites, Z″o is complex impedance at resonance.
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Overlapping of the curves indicates temperature independent dynamical process in the system. Fig. 9(Color online) (a) ln(τ)vs. 103/T curves for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO –
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0.9PZT nanocomposites. σdc vs. 103/T curves for (c) 0.05LSMO – 0.95PZT and (d) 0.1LSMO – 0.9PZT nanocomposites. The Ea obtained from both the curves indicates both relaxation and conductivity processes are determined by same type of charge carriers. Red solid lines show the fitted curve.
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Fig. 10(Color online) σac vs. f at different temperatures for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO – 0.9PZT nanocomposites, which shows that conductivity increases with increase in temperatures and f. Red solid lines show the fitted curve.
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Fig. 11(Color online) n and p as a function of temperatures for (a) 0.05LSMO – 0.95PZT and (b) 0.1LSMO – 0.9PZT nanocomposites, which shows that conductivity determined by both small
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and large polarons hopping mechanism.
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Table I: Fitted parameters obtained from Z″ vs. f curves at different magnetic fields for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites.
500 1000
Cgb2 (nF) 7.07 (±0.01) 14.11 (±0.01) 8.00 (±0.05) 7.51 (±0.01)
Rgb1 (kΩ) 689.51 (±0.01) 674.33 (±0.01) 651.98 (±0.02) 640.72 (±0.02)
0.1LSMO – 0.9PZT Cgb1 Rgb2 (nF) (MΩ) 0.76 1.04 (±0.01) (±0.01) 0.80 1.15 (±0.01) (±0.01) 0.81 1.16 (±0.01) (±0.01) 0.84 1.29 (±0.02) (±0.01)
Cgb2 (nF) 7.76 (±0.01) 7.14 (±0.01) 6.29 (±0.03) 6.87 (±0.01)
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0.05LSMO – 0.95PZT Cgb1 Rgb2 (nF) (MΩ) 1.08 1.30 (±0.01) (±0.01) 1.00 1.11 (±0.01) (±0.01) 1.01 0.90 (±0.01) (±0.01) 1.03 0.93 (±0.01) (±0.01)
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0
Rgb1 (kΩ) 870.02 (±0.03) 807.63 (±0.01) 547.92 (±0.01) 530.14 (±0.01)
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H (Oe)
Table II: Fitted parameters obtained from Z″ vs. f curves at different temperatures for 0.05LSMO – 0.95PZT and 0.1LSMO – 0.9PZT nanocomposites.
100 150 200
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50
0.05LSMO – 0.95PZT Cgb1 Rgb2 (nF) (MΩ) 3.69 1.54 (±0.03) (±0.02) 8.17 1.62 (±0.08) (±0.03) 16.81 0.23 (±0.02) (±0.02) 24.16 0.034 (±0.05) (±0.003) 27.30 0.008 (±0.02) (±0.001)
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Rgb1 (kΩ) 120.14 (±0.05) 36.39 (±0.01) 1.68 (±0.01) 0.71 (±0.02) 0.30 (±0.04)
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T (oC)
Cgb2 (nF) 4.66 (±0.01) 23.37 (±0.01) 50.96 (±0.02) 27.14 (±0.03) 35.64 (±0.05)
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Rgb1 (kΩ) 483.88 (±0.01) 246.48 (±0.01) 163.55 (±0.01) 4.98 (±0.01) 1.68 (±0.01)
0.1LSMO – 0.9PZT Cgb1 Rgb2 (nF) (MΩ) 1.81 0.79 (±0.01) (±0.01) 2.60 0.35 (±0.01) (±0.01) 4.31 0.056 (±0.02) (±0.002) 3.56 0.010 (±0.01) (±0.001) 3.56 0.0030 (±0.01) (±0.0002)
Cgb2 (nF) 9.46 (±0.01) 8.71 (±0.01) 5.96 (±0.03) 26.96 (±0.01) 27.07 (±0.01)
I (arb. unit) 165
110
100 *
*
55
0 20 *
*
40
Fig. 1
(220)
(211)
(120)
(a) 0.05LSMO - 0.95 PZT *PZT + LSMO
* *
U*,+S (130, 341) CR IP T
0
(020)
(110)
*
*
*
*
*
*
2 (degree) 60
*,+ (130, 341)
200
*,+ (111, 211)
(010)
300
AC *, + (111, 211)(110) C E (020) P (120) T ED (211) M AN (220)
(010)
I (arb. unit)
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(b)
0.1LSMO - 0.9PZT
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xLSMO - (1-x)PZT
x = 0.05
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(d)
2
TE D 0
H (kOe)
1
20
0 15
0.07 0.00
10
-0.07
EP δE
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-1
40
H= 800 Oe
0.14 xLSMO -(1-x)PZT
P (C/cm )
E33 (mV/cm-Oe)
(b)
0.0
E33
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Hac
-0.8 0.5
-2
E31
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-0.5
(c) 60
E (mV/cmOe)
(a)
f = 10 Hz x = 0.05 x = 0.1
-0.14 -88
-44
0
E (V/cm)
H Hac
44
88
5
x = 0.1 H= 600 Oe
0 2
0
Fig. 2
5
E (mV/cmOe)
xLSMO - (1-x)PZT x= 0.05, 2 kHz x= 0.1, 1 kHz
δE
E31 (mV/cm-Oe)
0.8
10
f (kHz)
15
20
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0.05LSMO - 0.95PZT
0.05LSMO - 0.95PZT
(c)
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ML (%)
1080
0.05LSMO - 0.95PZT
4
1 kHz 2 kHz
0 Oe 300
600
H (Oe)
0.2
900
0.1
0
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MD (%)
0.1LSMO - 0.9PZT
300
600
300
600
H (Oe)
EP
4
10
5
10
6
10
0.0
0.0
0.05LSMO - 0.95PZT 1 kHz 2 kHz
-0.4
1.2
-0.8
0.8
-1.2 0
900
H (Oe)
0.1LSMO - 0.9PZT 3
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1 kHz 2 kHz
0
10
MD (%)
(d)
0.6
1500
2
1 kHz 2 kHz
1000 Oe
0.0
10
5
500 Oe
0.3
3000
0.05LSMO - 0.95PZT
0
50 Oe
900
0.3
10
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0
(b)
4500
0
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540
0 Oe 50 Oe 500 Oe 1000 Oe
0.4
15
MD (%)
8
tan
(a)
tan
1620
300
600
900
H (Oe)
0.4
0.1LSMO - 0.9PZT 2
10
3
10
4
10
f (Hz)
f (Hz)
Fig. 3
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6
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10
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5
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f (Hz)
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2
10
3
10
4
10
10
(d) 0.9
0.6
0.1LSMO - 0.9PZT 0.6
0.0 0.6
(b)
Rgb1
Rgb2
Cgb1
Cgb2
0.4
0.0
0.4
0.2
0.0
(f) 0.4
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EP
0.0 0.6 (c)
0.3
0.3
(e)
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0.2
0 Oe 50 Oe 500 Oe 1000 Oe Fit
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0.3
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0 Oe 50 Oe 500 Oe 1000 Oe Fit
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Z'(M)
0.05LSMO - 0.95PZT
Z"(M)
6
10
(a)
0.9
Z" (M)
5
10
0.2
0.0
0.0 0.0
0.3
0.6
Z' (M)
Z' (M)
4
Z" (M)
10
f (Hz)
3
0.9 0.0
0.2
Fig. 4
0.4
0.6
Z' (M)
0.8
Z" (M)
2
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(a)
Xm (%)
73 Hz 200 Hz
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-15
-30
-16
-20
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-35
-20
900
-25
(d)
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4
5 0.1LSMO - 0.9PZT
EP
73 Hz 200 Hz
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Xm (%)
7
3
4
6 5
73 Hz 200 Hz
4
0.1LSMO - 0.9PZT
300
300
600
H (Oe)
300
900
Fig. 5
600
H (Oe)
600
900
900
Zm (%)
(b)
0.1LSMO - 0.9PZT
Rm (%)
600
73 Hz 200 Hz
-24 5
300
0.05LSMO - 0.95PZT
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Rm (%)
0.05LSMO - 0.95PZT
-25
73 Hz 200 Hz
-12
-20
(c)
0.05LSMO - 0.95PZT
Zm (%)
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(c)
(a)
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30
tan
3
0
(b) 0.1LSMO - 0.9PZT
(d)
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0.1LSMO - 0.9PZT
9
6
EP
20
RT o 50 C o 100 C o 150 C o 200 C
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10
3
0 2
10
3
10
4
10
5
10
6
10
2
10
f (Hz)
3
10
4
10
f (Hz) Fig. 6
5
10
6
10
tan
8
6
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x 103
RT o 50 C o 100 C o 150 C o 200 C
4
x 103
0.05LSMO - 0.95PZT
0.05LSMO - 0.95PZT
12
9
10
2
6
10
4
10
(a)
10
5
6
10
10
RT o 50 C 0.01 o 100 C o 150 C o 200 C Fit 0.00
RT o 50 C 0.02 o 100 C o 150 C o 200 C Fit
0.5
f (Hz)
3
10
10
0.6
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Z' (M)
1.0
10
5
0.00
2
2
10
3
4
10
10
5
10
3
10
6
10
0.05LSMO - 0.95PZT
10
4
10
0.4 10
5
10
6
(d)
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0.1LSMO - 0.9PZT
0.0 0.6
0.0 (e)
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(b) 0.01
0.2 0.00 2
10
10
3
4
10
0.0 0.6
10
5
0.3
EP Z" (k)
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0.2
0.00 2
10
3
10
4
5
10
6
10
10
0.1
6
10
10
0.0
(f)
0.4
(c)
0
0.3
0
40 80 Z' (k)
4
Rgb1
Rgb2
Cgb1
Cgb2
Z" (k)
Z" (M)
0.4
0.01
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Z" (M)
0.02
0.4
0.2
0.2
2 0 0
0.0 0.0
0.2
0.4
Z' (M)
0.6
Z" (M)
10
4
0.8 0.0
Fig. 7
0.2
0.4
Z' (M)
6
Z' (k)
12
0.6
0.0
Z" (M)
3
Z' (M)
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f (Hz) 2
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f/fo
-1
0
10
10
1
10
10
4
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0.05LSMO - 0.95PZT
150oC
0.6
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200oC
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0.3
0.0
TE D
0.9
0.1LSMO - 0.9PZT
100oC
EP
0.6
(b)
150oC 200oC
AC C
Z"/Z"o
3
10
(a)
0.9
Z"/Z" o
2
10
0.3
0.0 -2
10
-1
10
0
10
1
10
f/fo
Fig. 8
2
10
3
10
4
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3
3
-1
10 /T (K ) 2.2
-1
10 /T (K )
2.4
2.2
2.6
2.4
2.6
-5.6
(c)
2
Ea
Parameters
Values
2.6
3
-1
lndc (cm)
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0.31
=
1.16
0.42
4.65
0.12 Ea/k
=
-5.38
0.16
2.4
2.6
2.8
-1
-10
-12
=
0.4
6e
V
-14
Error
Values
ln() 2
R = 0.998
R = 0.998
2.4
0.1LSMO - 0.9PZT
E
Error Parameters
2
2.2
-15
V
(d)
-20.66
AC C
-10
0.4
7e
0.49
ln() = ln() + E /k T ln(dc) = ln() - Ea/k T a
ln() = E /k = a
=
0.20
-5.44
TE D
V
EP
ln (s)
0.1LSMO - 0.9PZT
=
-1.17
a
Error
R = 0.997
(b)
e 0 4 0.
ln() = E /k = a
Values
E
-14
2
R = 0.994
-8
Parameters
Expt. Fit
-13
lndc (cm)
-6
ln(dc) = ln() - E /k T a
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-6.4 0.05LSMO - 0.95PZT Expt. Fit ln() = ln() + E /k T -7.2 a V Error Parameters e Values .40 0 1.02 ln() = -18.25 = a E -8.0 0.43 E /k = 4.69 a
0.05LSMO - 0.95PZT
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ln (s)
(a)
3.0
2.2
-1
-16 3
2.8
-1
10 /T (K )
10 /T (K )
Fig. 9
3.0
1E-4
0.1 0.01
1E-5
0.05LSMO - 0.95PZT (b)
5
10
TE D
AC C
EP
ac(cm)
0.01
1E-3
3
10
o
200 C
0.1LSMO - 0.9PZT
-1
0.1
II
I
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1E-3
1E-6
0.05LSMO - 0.95PZT III
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ac(cm)
-1
0.01
(a)
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1E-3
RT ACCEPTED MANUSCRIPT o 50 C o 100 C o 150 C o 200 C Fit
0.1
1E-4 1E-5
2
10
3
10
4
10
f (Hz) Fig. 10
5
10
6
10
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(c) 0.63 0.1LSMO - 0.9PZT
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(a)
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n
0.57
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0.6
(d)
TE D
0.5 (b) 2.0
1.99
EP
1.8
1.6 50
AC C
1.7
100
o
0.54 2.00
p
1.9
p
0.60
n
0.05LSMO - 0.95PZT
0.7
1.98
1.97 150
200
50
T ( C)
100
o
150
T ( C)
Fig. 11
200
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Highlights #Magnetoelectric response has been detected in these multiferroic nanocomposites at room.
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#Dielectric constant reveals Maxwell Wagner interfacial polarization at low frequency regime.
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#Field dependent impedance attributes depinning of domain walls at the grain boundaries.
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# Estimated activation energy indicates the same type of charge carrier for both the process.
#Conductivity follow Jonscher’s double power law attributes small and large polaronic
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hopping.