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Synthesis and characterization of Mg-Ag-Mn nano-ferrites for electromagnet applications
Physica B: Condensed Matter 569 (2019) 1–7
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Synthesis and characterization of Mg-Ag-Mn nano-ferrites for electromagnet applications
T
Rohit Jasrotiaa, Gagan Kumarb, Khalid Mujasam Batooc,∗, Syed Farooq Adild, Mujeeb Khand, Rajesh Sharmaa, Arun Kumare, Virender Pratap Singha,f,∗∗ a
School of Physics & Materials Science, Shoolini University, Solan, India Department of Physics, Chandigarh University, Gharuan, Punjab, India c King Abdullah Institute for Nanotechnology, College of Science, Building No.4, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia d Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia e Department of Physics and Materials Science, Himachal Pradesh University, Shimla, India f Department of Physics, GDC, Nerwa, Shimla, India b
A R T I C LE I N FO
A B S T R A C T
Keywords: Mg-Mn spinel ferrites Sol-gel method Structural properties FTIR Magnetic properties Mössbauer spectroscopy
In the present work, silver doped Mg–Mn ferrite nanoparticles (Mg1-yMnyAgxFe2-xO4; y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) are synthesized by using sol-gel technique and are characterized by x-ray diffraction (XRD), energy dispersive x-ray (EDX) analysis, field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) and Mössbauer spectroscopy. The single phase formation of the prepared ferrite nanoparticles is depicted by XRD study and the crystallite size as well as lattice parameter are found to increase (51–65 nm) and (8.367–8.384 Å) with the addition of silver ions. EDX study confirmed the compositional formation of the prepared ferrite nanoparticles. FESEM study depicted the clear crystalline nature of the nanoferrites with cubic structure. FTIR study revealed a decrease in bond length of M-O at tetrahedral (A) site and an increase in bond length between M-O at octahedral (B) site. The value of saturation magnetization is found to be 25.31 emu/gm for y = 0.1, x = 0 with highest value 30.26 emu/gm for ferrite with composition y = 0.4, x = 0.3. The cations distribution has been estimated using the XRD and magnetization techniques.
1. Introduction Ferrite materials which belong to a family of magnetic materials are technologically important materials due to their multifarious applications. The ferrite materials have their utility in various applications & devices like audio and video recording heads, loading coils, magnetic resonance imaging, inductors and transformers in telecommunication industry, magnetic fluids and hyperthermal cancer treatment, power transformer, antenna rods, satellite communication, choke coils, splitter applications, sensors and deflection yokes [1–4]. Thus, due to technological importance of ferrites in so many device applications, they have attracted the attention of material scientists for a long time. On the basis of magnetism, ferrites are categorized into two classes namely soft and hard ferrites while taking structure in to account, they are categorized into four classes namely spinel ferrites, garnets, magnetoplumbite and orthoferrites. All the above categories of ferrites are
∗
fascinating because of their broad range of industrial and technological applications. Fig. 1 shows the schematic picture of spinel ferrites having general formula MFe2O4 [5]. Spinel ferrites are generally represented as (M 2 +)[Fe23 +] O4 , where M2+ represents divalent metal ions or the mixture of divalent ions. A unit cell of spinel ferrite possesses 8 formula units i.e. (8 × MFe2O4). Therefore, a unit cell consists of 8 divalent metal ions, 16 Fe3+ ions and 32 O2− ions [6]. The 32 O2− ions are known to comprise a closed packed face centered cubic (FCC) arrangement which consists of 2 types of interstitial sites. One of interstitial site is known as tetrahedral site commonly called as A-site. This site is surrounded by 4 O2− ions. Second interstitial site is called as octahedral site commonly abbreviated as B-site. This site is enclosed by 6 O2− ions. In spinel ferrites, there are 64 A-sites and 32 B-sites. Out of 64 A-sites and 32 B-sites cations only engage 8 A-sites and 16 B-sites respectively [7]. In spinel ferrites, the general division of metal ions over A-site and B-site can be expressed as (M12−+x Fex3 +)[Mx2 +Fe23−+x ] O42 −,
Corresponding author. Corresponding author. School of Physics & Materials Science, Shoolini University, Solan, India. E-mail addresses: [email protected] (K.M. Batoo), [email protected] (V.P. Singh).
∗∗
https://doi.org/10.1016/j.physb.2019.05.033 Received 7 March 2019; Received in revised form 14 May 2019; Accepted 20 May 2019 Available online 21 May 2019 0921-4526/ © 2019 Elsevier B.V. All rights reserved.
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Fig. 1. Schematic structure of spinel ferrites.
grade with 99% purity were taken in a stoichiometric ratio and dissolved in deionized water and stirred on a hot plate. When the nitrates dissolved completely in the deionized water, the citric acid in 1:1 M ratio was added to the nitrate solution and continuously stirred on a hot plate. The ammonia was added to the solution in a dropwise manner so as to maintain the pH 7. In order to have the gel formation; the solution was heated with constant stirring at 100 °C until a powder was formed. The obtained powder was then sintered at 1000 °C for 5 h to have the final product. The single phase study of the synthesized nanoferrites was done with the help of XPERT PRO x-ray diffractometer using Cu kα radiation. The field emission scanning electron microscopy (FESEM) was carried out using Hitachi model SU8010. The FTIR study was carried out with the help of PerkinElmer spectrometer (Spectrum-400 FTIR). The M-H study was carried out using Vibrating Sample Magnetometer (Model - EV9) and the Mössbauer spectroscopy was carried out using FAST Com Tec 07090 and the spectra were analyzed with the help of Moss Win 4.0 software.
where parenthesis indicates the cations present at A-site while the square bracket indicates the cations present at B-site. Thus, the capability to allocate the metal ions on A-site and B-site make ferrites very interesting materials where a material scientist can play with the properties of ferrites. Y. Slimani et al. [7] have synthesized Li2xCu1xAlyFe2-yO4 nanoferrites via hydrothermal method and has investigated for structural, FTIR and magnetic properties. M. Nazrul Islam et al. [8] have developed Mn0.5Ni0.1Zn0.4Fe2−xGdxO4 ferrites by solid state reaction method and have studied the structural, electric and magnetic properties. Infact there are many spinel ferrites like Ni–Zn, Mn–Zn ferrites etc. but in addition to these Mg–Mn ferrite is one of the category of spinel ferrites which have a broad range of device applications. In view of same we have focused our self to study the doped Mg–Mn nanoferrites. In past, several researchers have studied the substituted Mg–Mn ferrites [9–18]. M. Singh et al. [9] have investigated the irradiation effects on the structural, dielectric and permeability properties of In3+ substituted Mg–Mn ferrites. S. Ghosh et al. [10] have carried out the positron annihilation and Mössbauer studies of MgMn0.1Fe1.9−xInxO4 ferrites in bulk and nano form. B. S. Chauhan et al. [11] have reported the magnetic properties of Mg–Mn ferrites developed by citrate precursor method. A. Lakshman et al. [12] have presented the electric, dielectric and magnetic properties of mixed Mg–Mn ferrites. S. K. Sharma et al. [13] have synthesized the Mg–Mn nanoparticles via solid state reaction technique and studied the variation in magnetic properties due to irradiation. S. Kumar et al. [14] have studies the effects Ti4+ substitution on the electrical and magnetic properties of Mg–Mn ferrites. Gagan Kumar et al. [15] have studied the temperature dependent electrical properties of Gd3+ substituted Mg–Mn nanoferrites. N. Lwin et al. [16] have presented the structural and electromagnetic properties of Mg–Mn ferrites doped with thulium ions. N. Lwin et al. [17] have presented the structural, magnetic & electromagnetic properties of Gd3+ doped Mg–Mn nanoferrites. In fact many researchers have studied the doped Mg–Mn ferrites in bulk and nano form but no literature is available on the structural, magnetic and optical study of silver doped Mg–Mn nanoferrites synthesized via solgel technique. Therefore, in this work we have synthesized silver doped Mg–Mn nanoferrites by sol-gel technique and then investigated the structural optical and magnetic properties.
3. Results and discussions 3.1. Structural and morphological study Fig. 2 shows the x-ray diffraction patterns of Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) ferrite nanoparticles. The diffraction peaks obtained from the planes confirmed the single phase cubic spinel structure of the synthesized nanoferrites. The obtained hkl values are found to be consistent with JCPDS Card No17-0464. Further, for 0.2 ≤ x ≤ 0.4, the XRD study indicated the presence of additional peak at around 43° which may be due to the difference in the ionic radius of Ag+ and Fe3+ ions or either the difference between the ionic radius of Mg2+ and Mn2+ ions. A similar spinel phase peak at around 43° in the XRD has been reported by C. F. Zhang et al. [18] for the substitution of cobalt in the Mn–Zn ferrite matrix. The crystallite size of the synthesized samples is calculated with the help of Scherrer's formula [19]:
t=
0.9λ βcosθ
(1)
Where λ is the wavelength of x-ray radiation, β is full width at half maxima and θ is the Bragg's angle. The calculated values of crystallite size are given in Table 1. The lattice parameter was investigated with the help of following relation [19]:
2. Experimental procedure The ferrite nanoparticles with composition Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized using sol-gel technique. The hydrated metal nitrates Mg (NO3)2.6H2O, Mn(NO3)2.4H2O, Ag(NO3).xH2O & Fe(NO3).9H2O of AR
a = dhkl h2 + k 2 + l 2
(2)
where dhkl is the observed interplanar distance for hkl planes. The d 2
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Fig. 2. X-ray diffraction patterns of Mg1-yMnyAgxFe2-xO4 nanoferrites.
spacing values are calculated for the recorded peaks with the help of Bragg's law and the values of lattice parameter are tabulated in Table 1. The lattice parameter is observed to increase (8.367–8.384 Å) with the addition of Ag+ ions as well as Mn2+ ions. The same is due to the difference in the ionic radius of the Mg2+, Mn2+, Ag+ and Fe3+ ions. As the ionic radius of Ag+ ions (1.26 Å) and Mn2+ ions (0.91 Å) is higher than the ionic radius of Fe3+ ions (0.67 Å) and Mg2+ ions (0.78 Å) therefore, the addition of Ag+ ions and Mn2+ ions has resulted an increase in lattice parameter. The x-ray density and hopping lengths in tetrahedral sites (LA) and octahedral sites (LB) are calculated by using the following relation [1,19] and the calculated values are tabulated in Table 1:
8M N a3
ρx−ray =
Fig. 3. FESEM images for Mg1-yMnyAgxFe2-xO4 nanoferrites (a) y = 0.1, x = 0.0. (b) y = 0.2, x = 0.1 (c) y = 0.3, x = 0.2 (d) y = 0.4, x = 0.3 (e) y = 0.5, x = 0.4.
nanoparticles and the EDX spectra are shown in Fig. 4. The compositional percentage of Mg2+, Mn2+, Fe3+, Ag+ and O2− ions are given in Table 2 which confirmed the non existence of impurity phase as well as predicted all the ions are in good stoichiometric proportions as desired. The cation distribution is estimated by using the method suggested by the Bertaut [20] as well as Weil, Bertaut and Bochirol [21]. In present work, the reflections (2 2 0), (4 0 0) and (4 4 0) have been used to calculate the intensity ratio because it has been reported [22] that the intensity ratios of planes I220/I400, I400/I440 and I220/I440 are very sensitive for the cation distribution. The x-ray intensity for different planes (Ihkl) is calculated by using the following formula [23]:
(3)
LA = a
3 4
(4)
LB = a
2 4
(5)
where M is the molecular weight of the sample, N is the Avogadro's number and a is the lattice parameter. The x-ray density as well as hopping length at tetrahedral and octahedral sites are observed to increase (4.61–5.32 g/cm3), (3.619–3.630 Å) and (2.956–2.964 Å) with the addition of Ag+ ions as well as Mn2+ ions. The increase in hopping lengths is due the increase in lattice parameter while the increase in xray density is because of the increase in molecular weight as compared to the increase in lattice parameter. Fig. 3 shows the FESEM images for Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) ferrite nanoparticles. The micrographs of the samples confirmed that nanoferrites are cubic in shape, dense with uniform distribution. The energy dispersive x-ray spectroscopy has been carried out to validate the chemical composition and stoichiometric proportions of Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2 and x = 0.0, 0.1) ferrite
Ihkl = |F|2hkl . P. Lp
(6)
where F is structure factor, P is the multiplicity factor and Lp is the Lorentz polarization factor. The Lorentz polarization factor was calculated by using the following relation [23]:
Lp = (
1 + cos 22θ ) sin2θ cosθ
(7)
The structure factors for different planes are calculated by using the relation as reported by Furuhashi et al. [24]. The multiplicity and ionic scattering factors are taken from the literature of B.D. Cullity [25]. The estimated values of cation distribution for Mg1-yMnyAgxFe2-xO4 nanoferrites are tabulated in Table 3. It is evident to the table that observed and calculated intensity ratios are consistent with each other. Further,
Table 1 Variation of crystallite size, lattice parameter, x-ray density and hopping lengths for Mg1-yMnyAgxFe2-xO4 nanoferrites. Sample y = 0.1, y = 0.2, y = 0.3, y = 0.4, y = 0.5,
x = 0.0 x = 0.1 x = 0.2 x = 0.3 x = 0.4
Interplanar spacing (Å)
Crystallite size (nm)
Lattice parameter (Å)
x-ray density (g/cm3)
LA (Å)
LB (Å)
2.523 2.525 2.526 2.527 2.528
57 65 60 51 54
8.367 8.376 8.382 8.383 8.384
4.61 4.78 4.96 5.14 5.32
3.619 3.624 3.628 3.629 3.630
2.956 2.959 2.962 2.963 2.964
3
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to have two absorption bands (υ1 and υ2) in which the higher frequency absorption band (υ1) is located in the range of 604.3–651.5 cm−1 and the lower frequency absorption band (υ2) is located in the range of 439.7–452.07 cm−1 thereby confirming spinel structure formation of the synthesized nanoferrites. The difference in frequencies of bands υ1 and υ2 is due to changes in the bond length Fe2+-O2- at tetrahedral and octahedral sites. In the present research work, it is depicted that the frequency of two absorption bands decrease with increase in Ag content as given in Table 3 which may be due to the mixed cationic distribution. It is to be emphasized that the absorption bands between 3200 and 3800 cm−1 may have multiple peaks which can be resolved through convolution. The relative percentage transmission is found to be higher in the case of x = 0.3 and x = 0.4 nanoferrites which is due to higher Ag+ concentration. 3.3. Magnetic study Fig. 6 shows the variation of magnetization as a function of applied magnetic field. The obtained magnetic parameters like saturation magnetization, retentivity, coercivity and squareness ratio are tabulated in Table 5. The saturation magnetization is found to increase with the increasing substitution of Mn2+ and Ag+ ions up to y = 0.4, x = 0.3 and is observed to decrease thereafter. The variation of saturation magnetization (Ms) as a function of Mn and Ag content can be explained on the basis of difference in magnetic moments and exchange interaction at the A-site and B-site [26]. According to previous literature, three types of interactions such as A-A interaction (interaction between ions both at A-site and A-site), B–B interaction (interaction between ions both at B-site and B-site) and A-B interaction (interaction between ions at A-site and B-site) exists between the different ions inside the unit cell of the crystal lattice. It has been observed that A-B interaction aligns all the spins of magnetic ions at the tetrahedral site (A-site) in one direction while in opposite direction at the octahedral site (B-site) therefore the net magnetization is given as below:
Fig. 4. EDX spectra for Mg1-yMnyAgxFe2-xO4 nanoferrites (a) y = 0.1, x = 0.0 (b) y = 0.2, x = 0.1.
Table 2 Elemental percentage in Mg1-yMnyAgxFe2-xO4 nanoferrites. Sample
O2− (%)
Mg2+ (%)
Mn2+ (%)
Fe3+ (%)
Ag+ (%)
y = 0.1, x = 0.0 y = 0.2, x = 0.1
37.16 45.27
10.02 10.65
2.52 2.86
50.30 41.20
0 0.09
(8)
M= MB − MA
where MA and MB are magnetization of A and B sub-lattices respectively. The increase in magnetization due to the increase in Ag concentration up to x = 0.3 may be because of the fact that Ag+ ions enter into the tetrahedral site (A-site) and replace Fe3+ ions due to which magnetization of A sub-lattice decreases. However, a decrease in magnetization for x = 0.4 may be due to the occupancy of octahedral site by some of the Ag+ ions due to which reduced the magnetization at octahedral site to a small extent which has then resulted an overall decrease in the magnetization. The variation of magnetization as a function of applied magnetic field suggested that for small concentration of Ag+ ions there is a strengthening of the exchange interaction in the Mg–Mn ferrite nano matrix. The obtained values of magnetization and retentivity in the present work are further suggesting the utility of synthesized nanoferrites for electromagnet applications. The coercivity is observed to increase (9.11–52.42 Oe) up to y = 0.4 and x = 0.3 and decreases to 46.45 Oe thereafter. The coercivity (Hc) depends upon various parameters such as particle size, morphology, micro-strain and magneto-crystalline anisotropy. In general, for material with single
the cation distribution suggested that for 0 ≤ x ≤ 0.3, Ag+ ions preferred only tetrahedral (A) sites while for x = 0.4 some of the Ag+ ions also occupied octahedral (B) sites. 3.2. FTIR study Fig. 5 shows the room temperature FTIR spectrum, recorded in the range 400 cm−1 to 4000 cm−1, for Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) ferrite nanoparticles. The absorption peaks are tabulated in Table 4. Two main broad metaloxygen bands are seen in the FTIR spectra of all the synthesized nanoferrites. The band υ1 around 600 cm−1 is attributed to the intrinsic vibration of tetrahedral metal-oxygen complexes and the band υ2 around 400 cm−1 is attributed to the intrinsic vibration of octahedral metal-oxygen complexes. In the present work, the spectra are observed
Table 3 Cation distribution in Mg1-yMnyAgxFe2-xO4 nanoferrites inferred from the X-ray diffraction studies. x
0.0 0.1 0.2 0.3 0.4
Cation distribution
(Mg0.451Mn0.099Fe0.849)A [Mg0.449Mn0.001Fe1.151]B (Mg0.451Mn0.164Ag0. 1Fe0.773)A [Mg0.349Mn0.036Fe1.127]B (Mg0.451Mn0.292Ag0. 2Fe0.622)A [Mg0.249Mn0.008Fe1.178]B (Mg0.451Mn0.393Ag0. 3Fe0.498)A [Mg0.149Mn0.007Fe1.202]B (Mg0.451Mn0.495Ag0. 398Fe0.388)A [Mg0.049Mn0.005Ag0. 002Fe1.212]B
I220/I400
I400/I440
I220/I440
Obs.
Cal.
Obs.
Cal.
Obs.
Cal.
1.60 1.05 1.08 1.06 1.03
1.56 1.01 1.05 1.03 1.01
0.71 0.91 0.95 0.96 0.99
0.69 0.88 0.94 0.94 0.94
1.14 0.96 1.03 1.02 1.01
1.09 0.89 0.99 0.97 0.95
4
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Fig. 5. FTIR spectra for Mg1-yMnyAgxFe2-xO4 nanoferrites.
domain, the coercivity increases with an increase in particle size while for material with multi domain structure, coercivity decreases with an increase in particle size. In the present work, coercivity is observed to increase (9.11–52.42 Oe) with an increase in the crystallite size and can be due to the role of either anisotropy or domain. The value of magneton number (nB) or magnetic moment for the synthesized nanoferrites is calculated by using the following relation [5]:
Table 4 Band positions for Mg1-yMnyAgxFe2-xO4 nanoferrites. Sample
y = 0.1, y = 0.2, y = 0.3, y = 0.4, y = 0.5, y = 0.1,
Absorption peaks
x = 0.0 x = 0.1 x = 0.2 x = 0.3 x = 0.4 x = 0.0
υ1
υ2
651.5 640.8 604.3 606.9 606.6 651.5
445.28 452.07 439.7 445.6 448 445.28
nB =
Ms × M.W 5585
(9)
where Ms and M.W. are saturation magnetization and molecular weight of the synthesized samples respectively. The values of magnetic moment are given in Table 6. The magnetic moment shows the same behaviour as observed for the magnetization. The magnetic moment increases due to the increase in the saturation magnetization as well as molecular weight of synthesized samples and these both are in good agreement with each other. Further, the cation distribution obtained using XRD technique has been also verified with the help of magnetization method [6] using eq. (8) and eq. (9). Table 6 represents the observed values of magnetic moments and the values calculated from the estimated cation distribution. It is evident to Table 6 that the observed and calculated values agree reasonably well with each other suggesting that the cation distribution obtained by using the XRD method is principally acceptable. 3.4. Mössbauer study Fig. 7 shows the room temperature Mössbauer spectra for Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) ferrite nanoparticles and the obtained Mössbauer parameters are given in Table 7. The basic three types of Mössbauer parameters viz isomer shift (δ), electrical quadrupole splitting (Nuclear electric quadrupole splitting) and hyperfine field (Hf) gives the information about the valence band, magnetic ordering and cation distribution. The spectra of the synthesized samples indicate six merged line patterns indicating magnetic ordering as well as ferrimagnetic phase. It depicts that the
Fig. 6. Variation of magnetization as a function of applied field for Mg1nanoferrites.
yMnyAgxFe2-xO4
5
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Table 5 Saturation magnetization, retentivity, coercivity and squareness ratio for Mg1-yMnyAgxFe2-xO4 nanoferrites. Sample
y = 0.1, y = 0.2, y = 0.3, y = 0.4, y = 0.5,
x = 0.0 x = 0.1 x = 0.2 x = 0.3 x = 0.4
Saturation Magnetization (Ms) (emu/g)
Remanence Magnetization (Mr) (emu/g)
Coercivity (Hc) (Oe)
Squareness ratio (Mr/Ms)
25.31 26.62 28.10 30.26 28.78
0.40 1.10 2.30 2.79 2.27
9.11 23.53 46.69 52.42 46.45
0.02 0.04 0.08 0.09 0.08
of nuclear energy levels between the source and absorber due to electrostatic interaction between the nucleus and electron in a solid and only s-electron wave functions have definite value at the nucleus which, therefore, responsible for the electrostatic interaction.We know that bond separation between Fe3+ and O2− in case of spinel cubic nanoferrites is larger at the octahedral site as compared to tetrahedral site which depicted from Table 5 that IS (B) > IS (A) indicating isomer shift at octahedral site is more than that at tetrahedral site. Since the bond separation between iron and oxygen is more at octahedral site due to which overlapping of Fe3+ ions is smaller at octahedal site and therefore, have large isomer shift. The hyperfine field of two magnetic sextets for the synthesized spinel cubic nanoferrites is found to be vary from 53.55 to 51.46834 T at A-site and 50.58178 to 47.12874 T. The broadening of line width at the A-site is increasing while at B-site, decreasing with increasing the content of silver ions. In addition to this, non-zero and less value of quadrupole splitting in the present research work indicating the presence of only Fe3+ charge states [27].
Table 6 Cation distribution in Mg1-yMnyAgxFe2-xO4 nanoferrites estimated from magnetization studies. x
0.0 0.1 0.2 0.3 0.4
Cation distribution
nB (μB)
(Mg0.451Mn0.099Fe0.849)A [Mg0.449Mn0.001Fe1.151]B (Mg0.451Mn0.164Ag0. 1Fe0.773)A [Mg0.349Mn0.036Fe1.127]B (Mg0.451Mn0.292Ag0. 2Fe0.622)A [Mg0.249Mn0.008Fe1.178]B (Mg0.451Mn0.393Ag0. 3Fe0.498)A [Mg0.149Mn0.007Fe1.202]B (Mg0.451Mn0.495Ag0. 398Fe0.388)A [Mg0.049Mn0.005Ag0. 002Fe1.212]B
Obs.
Cal.
0.92 1.01 1.10 1.23 1.22
0.92 1.01 1.09 1.23 1.21
hyperfine field (Hf) experienced by Fe3+ ions at B-site is higher than that of A-site values. The black dot shows the experimental data and the solid red coloured curve between the two magnetic sextets represents the best fitted curve of the experimental data of the synthesized samples. These two magnetic sextets found in spectra correspond to two interstitial sites (A-site & B-site) present in the lattice. The internal magnetic field (Hint) arises due to various interactions can be expressed by following equation:
Hint = Hcore + HSTHF + HTHF +
HD
4. Conclusions The silver doped magnesium-manganese nanoferrites are successfully synthesized by sol-gel technique. The XRD patterns confirmed the formation of cubic single phase without any additional impurity peaks. The lattice parameter and x-ray density were observed to increase with the addition of Mn2+ and Ag + ions. FESEM study depicted the cubical nature of the synthesized nanoferrites having uniform distribution. EDS
(10)
where Hcore is the field owing due to polarization of core s-electrons, HSTHF and HTHF are the super transferred and transferred fields respectively and HD is the dipolar field. The isomer shift (δ) is the shifting
Fig. 7. Mössbauer spectra for Mg1-yMnyAgxFe2-xO4 nanoferrites. 6
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Table 7 Mössbauer parameters for Mg1-yMnyAgxFe2-xO4 nanoferrites. Sample
y = 0.1, x = 0.0 y = 0.3, x = 0.2 y = 0.5, x = 0.4
Line Width (mm/s)
Isomer Shift (mm/s)
Quadrupole Splitting (mm/s)
Hyperfine Field ‘Hf’
A
B
A
B
A
B
A
B
0.36 0.43 0.66
0.77 0.67 0.61
0.19 0.18 0.07
0.24 0.22 0.19
0.021 0.087 0.013
0.045 0.018 −0.185
53.55 53.18 51.47
50.58 50.48 47.13
study depicted the desired stoichiometric ratio of the involved ions. FTIR study indicated two absorption peaks in the range of 400–700 cm−1 with the substitution of silver ions. The estimated values of cations distributions suggested that for 0 ≤ x ≤ 0.3, Ag+ ions prefer to occupy A-sites while for x = 0.4, Ag+ ions also occupied B-sites. The magnetic study indicated the strengthening of the exchange interactions for the low concentration of the Ag+ ions. The observed values of magnetization and retentivity suggested the utility of the synthesized nanoferrites for electromagnet applications.
[7] Y. Slimani, H. Güngüneş, M. Nawaz, A. Manikandan, H.S. El Sayed, M.A. Almessiere, H. Sözeri, S.E. Shirsath, I. Ercan, A. Baykal, Ceram. Int. 44 (2018) 14242. [8] M. Nazrul Islam, A.K.M. Akther Hossain, J. Mater. Res. Technol. 8 (2019) 208. [9] M. Singh, A. Dogra, R. Kumar, Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. Atoms 196 (2002) 315. [10] S. Ghosh, P.M.G. Nambissan, R. Bhattacharya, Phys. Lett. 325 (2004) 301. [11] B.S. Chauhan, R. Kumar, K.M. Jadhav, M. Singh, J. Magn. Magn. Mater. 283 (2004) 71. [12] A. Lakshman, P.S.V. Subba Rao, B.P. Rao, K.H. Rao, J. Phys. D Appl. Phys. 38 (2005) 673. [13] S.K. Sharma, R. Kumar, V.V. Siva Kumar, M. Knobel, V.R. Reddy, A. Gupta, M. Singh, Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. Atoms 248 (2006) 37. [14] S. Kumar, Ravi Kumar, S.K. Sharma, V.R. Reddy, A. Banerjee, Alimuddin, Solid State Commun. 142 (2007) 706. [15] Gagan Kumar, J. Shah, R.K. Kotnala, V.P. Singh, M. Dhiman, S.E. Shirsath, M. Shahbuddin, K.M. Batoo, M. Singh, J. Magn. Magn. Mater. 390 (2015) 50. [16] N. Lwin, R. Othman, S. Sreekantan, M.N.A. Fauzi, J. Magn. Magn. Mater. 385 (2015) 433. [17] N. Lwin, M.N.A. Fauzi, S. Sreekantan, R. Othman, Phys. B Condens. Matter 461 (2015) 134. [18] C.F. Zhang, X.C. Zhong, H.Y. Yu, Z.W. Liu, D.C. Zeng, Physica B 404 (2009) 2327. [19] Gagan Kumar, Ritu Rani, Sucheta Sharma, Khalid M. Batoo, M. Singh, Ceram. Int. 39 (2013) 4813. [20] E.F. Bertaut, C. R. Hebd. Seances Acad. Sci. 230 (1950) 213–215. [21] L. Weil, E.F. Bertaut, L. Bochirol, J. Phys. Radium 11 (1950) 208–212. [22] S.S. More, R.H. Kadam, A.B. Kadam, A.R. Shite, D.R. Mane, K.M. Jadhav, J. Alloy. Comp. 502 (2010) 477. [23] P. Porta, F.S. Stone, R.G. Turner, J. Solid State Chem. 11 (1974) 135. [24] H. Furuhashi, M. Inagaki, S. Naka, J. Inorg. Nucl. Chem. 35 (1973) 3009. [25] B.D. Cullity, Elements of X-Ray Diffraction, Addison Wesley, USA, 1956, p. 474. [26] M.H. Khedr, M. Bahgat, W.M.A. El Rouby, Mater. Technol. 23 (2008) 27. [27] Gagan Kumar, R.K. Kotnala, J. Shah, V. Kumar, A. Kumar, P. Dhiman, M. Singh, Phys. Chem. Chem. Phys. 19 (2017) 16669.
Acknowledgement The author V. P. Singh is thankful to Indian agency DRDO for its constant support and funding through the whole research work (Project No. ERIP/PR/1303129/M/01/1564). Authors K.M. Batoo, and S. F. Adil are thankful to the Deanship of Scientific Research at King Saud University for its funding through the Research Group Project No. RG1437-030. References [1] Anjana Sharma, M. Khalid, E.H. Batoo, Raslan S.F. Adil, Gagan Kumar, Vacuum 157 (2018) 422. [2] A. Goldman, Modern Ferrite Technology, Springer Science & Business Media, 2006. [3] S.F. Mansour, M.A. Elkestawy, Ceram. Int. 37 (2011) 1175. [4] M.A. Ahmed, Samiha T. Bishay, S.I. El-dek, G. Omar, J. Alloys Compds. 509 (2011) 7891. [5] V.P. Singh, Himachal Pradesh University, Shimla, India, Ph.D. Thesis (2017). [6] Gagan Kumar, J. Shah, R.K. Kotnala, V.P. Singh, Sarveena, G. Garg, S.E. Shirsath, K.M. Batoo, M. Singh, Mater. Res. Bull. 63 (2015) 216.
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Physica B: Condensed Matter journal homepage: www.elsevier.com/locate/physb
Synthesis and characterization of Mg-Ag-Mn nano-ferrites for electromagnet applications
T
Rohit Jasrotiaa, Gagan Kumarb, Khalid Mujasam Batooc,∗, Syed Farooq Adild, Mujeeb Khand, Rajesh Sharmaa, Arun Kumare, Virender Pratap Singha,f,∗∗ a
School of Physics & Materials Science, Shoolini University, Solan, India Department of Physics, Chandigarh University, Gharuan, Punjab, India c King Abdullah Institute for Nanotechnology, College of Science, Building No.4, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia d Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia e Department of Physics and Materials Science, Himachal Pradesh University, Shimla, India f Department of Physics, GDC, Nerwa, Shimla, India b
A R T I C LE I N FO
A B S T R A C T
Keywords: Mg-Mn spinel ferrites Sol-gel method Structural properties FTIR Magnetic properties Mössbauer spectroscopy
In the present work, silver doped Mg–Mn ferrite nanoparticles (Mg1-yMnyAgxFe2-xO4; y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) are synthesized by using sol-gel technique and are characterized by x-ray diffraction (XRD), energy dispersive x-ray (EDX) analysis, field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) and Mössbauer spectroscopy. The single phase formation of the prepared ferrite nanoparticles is depicted by XRD study and the crystallite size as well as lattice parameter are found to increase (51–65 nm) and (8.367–8.384 Å) with the addition of silver ions. EDX study confirmed the compositional formation of the prepared ferrite nanoparticles. FESEM study depicted the clear crystalline nature of the nanoferrites with cubic structure. FTIR study revealed a decrease in bond length of M-O at tetrahedral (A) site and an increase in bond length between M-O at octahedral (B) site. The value of saturation magnetization is found to be 25.31 emu/gm for y = 0.1, x = 0 with highest value 30.26 emu/gm for ferrite with composition y = 0.4, x = 0.3. The cations distribution has been estimated using the XRD and magnetization techniques.
1. Introduction Ferrite materials which belong to a family of magnetic materials are technologically important materials due to their multifarious applications. The ferrite materials have their utility in various applications & devices like audio and video recording heads, loading coils, magnetic resonance imaging, inductors and transformers in telecommunication industry, magnetic fluids and hyperthermal cancer treatment, power transformer, antenna rods, satellite communication, choke coils, splitter applications, sensors and deflection yokes [1–4]. Thus, due to technological importance of ferrites in so many device applications, they have attracted the attention of material scientists for a long time. On the basis of magnetism, ferrites are categorized into two classes namely soft and hard ferrites while taking structure in to account, they are categorized into four classes namely spinel ferrites, garnets, magnetoplumbite and orthoferrites. All the above categories of ferrites are
∗
fascinating because of their broad range of industrial and technological applications. Fig. 1 shows the schematic picture of spinel ferrites having general formula MFe2O4 [5]. Spinel ferrites are generally represented as (M 2 +)[Fe23 +] O4 , where M2+ represents divalent metal ions or the mixture of divalent ions. A unit cell of spinel ferrite possesses 8 formula units i.e. (8 × MFe2O4). Therefore, a unit cell consists of 8 divalent metal ions, 16 Fe3+ ions and 32 O2− ions [6]. The 32 O2− ions are known to comprise a closed packed face centered cubic (FCC) arrangement which consists of 2 types of interstitial sites. One of interstitial site is known as tetrahedral site commonly called as A-site. This site is surrounded by 4 O2− ions. Second interstitial site is called as octahedral site commonly abbreviated as B-site. This site is enclosed by 6 O2− ions. In spinel ferrites, there are 64 A-sites and 32 B-sites. Out of 64 A-sites and 32 B-sites cations only engage 8 A-sites and 16 B-sites respectively [7]. In spinel ferrites, the general division of metal ions over A-site and B-site can be expressed as (M12−+x Fex3 +)[Mx2 +Fe23−+x ] O42 −,
Corresponding author. Corresponding author. School of Physics & Materials Science, Shoolini University, Solan, India. E-mail addresses: [email protected] (K.M. Batoo), [email protected] (V.P. Singh).
∗∗
https://doi.org/10.1016/j.physb.2019.05.033 Received 7 March 2019; Received in revised form 14 May 2019; Accepted 20 May 2019 Available online 21 May 2019 0921-4526/ © 2019 Elsevier B.V. All rights reserved.
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Fig. 1. Schematic structure of spinel ferrites.
grade with 99% purity were taken in a stoichiometric ratio and dissolved in deionized water and stirred on a hot plate. When the nitrates dissolved completely in the deionized water, the citric acid in 1:1 M ratio was added to the nitrate solution and continuously stirred on a hot plate. The ammonia was added to the solution in a dropwise manner so as to maintain the pH 7. In order to have the gel formation; the solution was heated with constant stirring at 100 °C until a powder was formed. The obtained powder was then sintered at 1000 °C for 5 h to have the final product. The single phase study of the synthesized nanoferrites was done with the help of XPERT PRO x-ray diffractometer using Cu kα radiation. The field emission scanning electron microscopy (FESEM) was carried out using Hitachi model SU8010. The FTIR study was carried out with the help of PerkinElmer spectrometer (Spectrum-400 FTIR). The M-H study was carried out using Vibrating Sample Magnetometer (Model - EV9) and the Mössbauer spectroscopy was carried out using FAST Com Tec 07090 and the spectra were analyzed with the help of Moss Win 4.0 software.
where parenthesis indicates the cations present at A-site while the square bracket indicates the cations present at B-site. Thus, the capability to allocate the metal ions on A-site and B-site make ferrites very interesting materials where a material scientist can play with the properties of ferrites. Y. Slimani et al. [7] have synthesized Li2xCu1xAlyFe2-yO4 nanoferrites via hydrothermal method and has investigated for structural, FTIR and magnetic properties. M. Nazrul Islam et al. [8] have developed Mn0.5Ni0.1Zn0.4Fe2−xGdxO4 ferrites by solid state reaction method and have studied the structural, electric and magnetic properties. Infact there are many spinel ferrites like Ni–Zn, Mn–Zn ferrites etc. but in addition to these Mg–Mn ferrite is one of the category of spinel ferrites which have a broad range of device applications. In view of same we have focused our self to study the doped Mg–Mn nanoferrites. In past, several researchers have studied the substituted Mg–Mn ferrites [9–18]. M. Singh et al. [9] have investigated the irradiation effects on the structural, dielectric and permeability properties of In3+ substituted Mg–Mn ferrites. S. Ghosh et al. [10] have carried out the positron annihilation and Mössbauer studies of MgMn0.1Fe1.9−xInxO4 ferrites in bulk and nano form. B. S. Chauhan et al. [11] have reported the magnetic properties of Mg–Mn ferrites developed by citrate precursor method. A. Lakshman et al. [12] have presented the electric, dielectric and magnetic properties of mixed Mg–Mn ferrites. S. K. Sharma et al. [13] have synthesized the Mg–Mn nanoparticles via solid state reaction technique and studied the variation in magnetic properties due to irradiation. S. Kumar et al. [14] have studies the effects Ti4+ substitution on the electrical and magnetic properties of Mg–Mn ferrites. Gagan Kumar et al. [15] have studied the temperature dependent electrical properties of Gd3+ substituted Mg–Mn nanoferrites. N. Lwin et al. [16] have presented the structural and electromagnetic properties of Mg–Mn ferrites doped with thulium ions. N. Lwin et al. [17] have presented the structural, magnetic & electromagnetic properties of Gd3+ doped Mg–Mn nanoferrites. In fact many researchers have studied the doped Mg–Mn ferrites in bulk and nano form but no literature is available on the structural, magnetic and optical study of silver doped Mg–Mn nanoferrites synthesized via solgel technique. Therefore, in this work we have synthesized silver doped Mg–Mn nanoferrites by sol-gel technique and then investigated the structural optical and magnetic properties.
3. Results and discussions 3.1. Structural and morphological study Fig. 2 shows the x-ray diffraction patterns of Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) ferrite nanoparticles. The diffraction peaks obtained from the planes confirmed the single phase cubic spinel structure of the synthesized nanoferrites. The obtained hkl values are found to be consistent with JCPDS Card No17-0464. Further, for 0.2 ≤ x ≤ 0.4, the XRD study indicated the presence of additional peak at around 43° which may be due to the difference in the ionic radius of Ag+ and Fe3+ ions or either the difference between the ionic radius of Mg2+ and Mn2+ ions. A similar spinel phase peak at around 43° in the XRD has been reported by C. F. Zhang et al. [18] for the substitution of cobalt in the Mn–Zn ferrite matrix. The crystallite size of the synthesized samples is calculated with the help of Scherrer's formula [19]:
t=
0.9λ βcosθ
(1)
Where λ is the wavelength of x-ray radiation, β is full width at half maxima and θ is the Bragg's angle. The calculated values of crystallite size are given in Table 1. The lattice parameter was investigated with the help of following relation [19]:
2. Experimental procedure The ferrite nanoparticles with composition Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized using sol-gel technique. The hydrated metal nitrates Mg (NO3)2.6H2O, Mn(NO3)2.4H2O, Ag(NO3).xH2O & Fe(NO3).9H2O of AR
a = dhkl h2 + k 2 + l 2
(2)
where dhkl is the observed interplanar distance for hkl planes. The d 2
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Fig. 2. X-ray diffraction patterns of Mg1-yMnyAgxFe2-xO4 nanoferrites.
spacing values are calculated for the recorded peaks with the help of Bragg's law and the values of lattice parameter are tabulated in Table 1. The lattice parameter is observed to increase (8.367–8.384 Å) with the addition of Ag+ ions as well as Mn2+ ions. The same is due to the difference in the ionic radius of the Mg2+, Mn2+, Ag+ and Fe3+ ions. As the ionic radius of Ag+ ions (1.26 Å) and Mn2+ ions (0.91 Å) is higher than the ionic radius of Fe3+ ions (0.67 Å) and Mg2+ ions (0.78 Å) therefore, the addition of Ag+ ions and Mn2+ ions has resulted an increase in lattice parameter. The x-ray density and hopping lengths in tetrahedral sites (LA) and octahedral sites (LB) are calculated by using the following relation [1,19] and the calculated values are tabulated in Table 1:
8M N a3
ρx−ray =
Fig. 3. FESEM images for Mg1-yMnyAgxFe2-xO4 nanoferrites (a) y = 0.1, x = 0.0. (b) y = 0.2, x = 0.1 (c) y = 0.3, x = 0.2 (d) y = 0.4, x = 0.3 (e) y = 0.5, x = 0.4.
nanoparticles and the EDX spectra are shown in Fig. 4. The compositional percentage of Mg2+, Mn2+, Fe3+, Ag+ and O2− ions are given in Table 2 which confirmed the non existence of impurity phase as well as predicted all the ions are in good stoichiometric proportions as desired. The cation distribution is estimated by using the method suggested by the Bertaut [20] as well as Weil, Bertaut and Bochirol [21]. In present work, the reflections (2 2 0), (4 0 0) and (4 4 0) have been used to calculate the intensity ratio because it has been reported [22] that the intensity ratios of planes I220/I400, I400/I440 and I220/I440 are very sensitive for the cation distribution. The x-ray intensity for different planes (Ihkl) is calculated by using the following formula [23]:
(3)
LA = a
3 4
(4)
LB = a
2 4
(5)
where M is the molecular weight of the sample, N is the Avogadro's number and a is the lattice parameter. The x-ray density as well as hopping length at tetrahedral and octahedral sites are observed to increase (4.61–5.32 g/cm3), (3.619–3.630 Å) and (2.956–2.964 Å) with the addition of Ag+ ions as well as Mn2+ ions. The increase in hopping lengths is due the increase in lattice parameter while the increase in xray density is because of the increase in molecular weight as compared to the increase in lattice parameter. Fig. 3 shows the FESEM images for Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) ferrite nanoparticles. The micrographs of the samples confirmed that nanoferrites are cubic in shape, dense with uniform distribution. The energy dispersive x-ray spectroscopy has been carried out to validate the chemical composition and stoichiometric proportions of Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2 and x = 0.0, 0.1) ferrite
Ihkl = |F|2hkl . P. Lp
(6)
where F is structure factor, P is the multiplicity factor and Lp is the Lorentz polarization factor. The Lorentz polarization factor was calculated by using the following relation [23]:
Lp = (
1 + cos 22θ ) sin2θ cosθ
(7)
The structure factors for different planes are calculated by using the relation as reported by Furuhashi et al. [24]. The multiplicity and ionic scattering factors are taken from the literature of B.D. Cullity [25]. The estimated values of cation distribution for Mg1-yMnyAgxFe2-xO4 nanoferrites are tabulated in Table 3. It is evident to the table that observed and calculated intensity ratios are consistent with each other. Further,
Table 1 Variation of crystallite size, lattice parameter, x-ray density and hopping lengths for Mg1-yMnyAgxFe2-xO4 nanoferrites. Sample y = 0.1, y = 0.2, y = 0.3, y = 0.4, y = 0.5,
x = 0.0 x = 0.1 x = 0.2 x = 0.3 x = 0.4
Interplanar spacing (Å)
Crystallite size (nm)
Lattice parameter (Å)
x-ray density (g/cm3)
LA (Å)
LB (Å)
2.523 2.525 2.526 2.527 2.528
57 65 60 51 54
8.367 8.376 8.382 8.383 8.384
4.61 4.78 4.96 5.14 5.32
3.619 3.624 3.628 3.629 3.630
2.956 2.959 2.962 2.963 2.964
3
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to have two absorption bands (υ1 and υ2) in which the higher frequency absorption band (υ1) is located in the range of 604.3–651.5 cm−1 and the lower frequency absorption band (υ2) is located in the range of 439.7–452.07 cm−1 thereby confirming spinel structure formation of the synthesized nanoferrites. The difference in frequencies of bands υ1 and υ2 is due to changes in the bond length Fe2+-O2- at tetrahedral and octahedral sites. In the present research work, it is depicted that the frequency of two absorption bands decrease with increase in Ag content as given in Table 3 which may be due to the mixed cationic distribution. It is to be emphasized that the absorption bands between 3200 and 3800 cm−1 may have multiple peaks which can be resolved through convolution. The relative percentage transmission is found to be higher in the case of x = 0.3 and x = 0.4 nanoferrites which is due to higher Ag+ concentration. 3.3. Magnetic study Fig. 6 shows the variation of magnetization as a function of applied magnetic field. The obtained magnetic parameters like saturation magnetization, retentivity, coercivity and squareness ratio are tabulated in Table 5. The saturation magnetization is found to increase with the increasing substitution of Mn2+ and Ag+ ions up to y = 0.4, x = 0.3 and is observed to decrease thereafter. The variation of saturation magnetization (Ms) as a function of Mn and Ag content can be explained on the basis of difference in magnetic moments and exchange interaction at the A-site and B-site [26]. According to previous literature, three types of interactions such as A-A interaction (interaction between ions both at A-site and A-site), B–B interaction (interaction between ions both at B-site and B-site) and A-B interaction (interaction between ions at A-site and B-site) exists between the different ions inside the unit cell of the crystal lattice. It has been observed that A-B interaction aligns all the spins of magnetic ions at the tetrahedral site (A-site) in one direction while in opposite direction at the octahedral site (B-site) therefore the net magnetization is given as below:
Fig. 4. EDX spectra for Mg1-yMnyAgxFe2-xO4 nanoferrites (a) y = 0.1, x = 0.0 (b) y = 0.2, x = 0.1.
Table 2 Elemental percentage in Mg1-yMnyAgxFe2-xO4 nanoferrites. Sample
O2− (%)
Mg2+ (%)
Mn2+ (%)
Fe3+ (%)
Ag+ (%)
y = 0.1, x = 0.0 y = 0.2, x = 0.1
37.16 45.27
10.02 10.65
2.52 2.86
50.30 41.20
0 0.09
(8)
M= MB − MA
where MA and MB are magnetization of A and B sub-lattices respectively. The increase in magnetization due to the increase in Ag concentration up to x = 0.3 may be because of the fact that Ag+ ions enter into the tetrahedral site (A-site) and replace Fe3+ ions due to which magnetization of A sub-lattice decreases. However, a decrease in magnetization for x = 0.4 may be due to the occupancy of octahedral site by some of the Ag+ ions due to which reduced the magnetization at octahedral site to a small extent which has then resulted an overall decrease in the magnetization. The variation of magnetization as a function of applied magnetic field suggested that for small concentration of Ag+ ions there is a strengthening of the exchange interaction in the Mg–Mn ferrite nano matrix. The obtained values of magnetization and retentivity in the present work are further suggesting the utility of synthesized nanoferrites for electromagnet applications. The coercivity is observed to increase (9.11–52.42 Oe) up to y = 0.4 and x = 0.3 and decreases to 46.45 Oe thereafter. The coercivity (Hc) depends upon various parameters such as particle size, morphology, micro-strain and magneto-crystalline anisotropy. In general, for material with single
the cation distribution suggested that for 0 ≤ x ≤ 0.3, Ag+ ions preferred only tetrahedral (A) sites while for x = 0.4 some of the Ag+ ions also occupied octahedral (B) sites. 3.2. FTIR study Fig. 5 shows the room temperature FTIR spectrum, recorded in the range 400 cm−1 to 4000 cm−1, for Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) ferrite nanoparticles. The absorption peaks are tabulated in Table 4. Two main broad metaloxygen bands are seen in the FTIR spectra of all the synthesized nanoferrites. The band υ1 around 600 cm−1 is attributed to the intrinsic vibration of tetrahedral metal-oxygen complexes and the band υ2 around 400 cm−1 is attributed to the intrinsic vibration of octahedral metal-oxygen complexes. In the present work, the spectra are observed
Table 3 Cation distribution in Mg1-yMnyAgxFe2-xO4 nanoferrites inferred from the X-ray diffraction studies. x
0.0 0.1 0.2 0.3 0.4
Cation distribution
(Mg0.451Mn0.099Fe0.849)A [Mg0.449Mn0.001Fe1.151]B (Mg0.451Mn0.164Ag0. 1Fe0.773)A [Mg0.349Mn0.036Fe1.127]B (Mg0.451Mn0.292Ag0. 2Fe0.622)A [Mg0.249Mn0.008Fe1.178]B (Mg0.451Mn0.393Ag0. 3Fe0.498)A [Mg0.149Mn0.007Fe1.202]B (Mg0.451Mn0.495Ag0. 398Fe0.388)A [Mg0.049Mn0.005Ag0. 002Fe1.212]B
I220/I400
I400/I440
I220/I440
Obs.
Cal.
Obs.
Cal.
Obs.
Cal.
1.60 1.05 1.08 1.06 1.03
1.56 1.01 1.05 1.03 1.01
0.71 0.91 0.95 0.96 0.99
0.69 0.88 0.94 0.94 0.94
1.14 0.96 1.03 1.02 1.01
1.09 0.89 0.99 0.97 0.95
4
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Fig. 5. FTIR spectra for Mg1-yMnyAgxFe2-xO4 nanoferrites.
domain, the coercivity increases with an increase in particle size while for material with multi domain structure, coercivity decreases with an increase in particle size. In the present work, coercivity is observed to increase (9.11–52.42 Oe) with an increase in the crystallite size and can be due to the role of either anisotropy or domain. The value of magneton number (nB) or magnetic moment for the synthesized nanoferrites is calculated by using the following relation [5]:
Table 4 Band positions for Mg1-yMnyAgxFe2-xO4 nanoferrites. Sample
y = 0.1, y = 0.2, y = 0.3, y = 0.4, y = 0.5, y = 0.1,
Absorption peaks
x = 0.0 x = 0.1 x = 0.2 x = 0.3 x = 0.4 x = 0.0
υ1
υ2
651.5 640.8 604.3 606.9 606.6 651.5
445.28 452.07 439.7 445.6 448 445.28
nB =
Ms × M.W 5585
(9)
where Ms and M.W. are saturation magnetization and molecular weight of the synthesized samples respectively. The values of magnetic moment are given in Table 6. The magnetic moment shows the same behaviour as observed for the magnetization. The magnetic moment increases due to the increase in the saturation magnetization as well as molecular weight of synthesized samples and these both are in good agreement with each other. Further, the cation distribution obtained using XRD technique has been also verified with the help of magnetization method [6] using eq. (8) and eq. (9). Table 6 represents the observed values of magnetic moments and the values calculated from the estimated cation distribution. It is evident to Table 6 that the observed and calculated values agree reasonably well with each other suggesting that the cation distribution obtained by using the XRD method is principally acceptable. 3.4. Mössbauer study Fig. 7 shows the room temperature Mössbauer spectra for Mg1-yMnyAgxFe2-xO4 (y = 0.1, 0.2, 0.3, 0.4, 0.5 and x = 0.0, 0.1, 0.2, 0.3, 0.4) ferrite nanoparticles and the obtained Mössbauer parameters are given in Table 7. The basic three types of Mössbauer parameters viz isomer shift (δ), electrical quadrupole splitting (Nuclear electric quadrupole splitting) and hyperfine field (Hf) gives the information about the valence band, magnetic ordering and cation distribution. The spectra of the synthesized samples indicate six merged line patterns indicating magnetic ordering as well as ferrimagnetic phase. It depicts that the
Fig. 6. Variation of magnetization as a function of applied field for Mg1nanoferrites.
yMnyAgxFe2-xO4
5
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Table 5 Saturation magnetization, retentivity, coercivity and squareness ratio for Mg1-yMnyAgxFe2-xO4 nanoferrites. Sample
y = 0.1, y = 0.2, y = 0.3, y = 0.4, y = 0.5,
x = 0.0 x = 0.1 x = 0.2 x = 0.3 x = 0.4
Saturation Magnetization (Ms) (emu/g)
Remanence Magnetization (Mr) (emu/g)
Coercivity (Hc) (Oe)
Squareness ratio (Mr/Ms)
25.31 26.62 28.10 30.26 28.78
0.40 1.10 2.30 2.79 2.27
9.11 23.53 46.69 52.42 46.45
0.02 0.04 0.08 0.09 0.08
of nuclear energy levels between the source and absorber due to electrostatic interaction between the nucleus and electron in a solid and only s-electron wave functions have definite value at the nucleus which, therefore, responsible for the electrostatic interaction.We know that bond separation between Fe3+ and O2− in case of spinel cubic nanoferrites is larger at the octahedral site as compared to tetrahedral site which depicted from Table 5 that IS (B) > IS (A) indicating isomer shift at octahedral site is more than that at tetrahedral site. Since the bond separation between iron and oxygen is more at octahedral site due to which overlapping of Fe3+ ions is smaller at octahedal site and therefore, have large isomer shift. The hyperfine field of two magnetic sextets for the synthesized spinel cubic nanoferrites is found to be vary from 53.55 to 51.46834 T at A-site and 50.58178 to 47.12874 T. The broadening of line width at the A-site is increasing while at B-site, decreasing with increasing the content of silver ions. In addition to this, non-zero and less value of quadrupole splitting in the present research work indicating the presence of only Fe3+ charge states [27].
Table 6 Cation distribution in Mg1-yMnyAgxFe2-xO4 nanoferrites estimated from magnetization studies. x
0.0 0.1 0.2 0.3 0.4
Cation distribution
nB (μB)
(Mg0.451Mn0.099Fe0.849)A [Mg0.449Mn0.001Fe1.151]B (Mg0.451Mn0.164Ag0. 1Fe0.773)A [Mg0.349Mn0.036Fe1.127]B (Mg0.451Mn0.292Ag0. 2Fe0.622)A [Mg0.249Mn0.008Fe1.178]B (Mg0.451Mn0.393Ag0. 3Fe0.498)A [Mg0.149Mn0.007Fe1.202]B (Mg0.451Mn0.495Ag0. 398Fe0.388)A [Mg0.049Mn0.005Ag0. 002Fe1.212]B
Obs.
Cal.
0.92 1.01 1.10 1.23 1.22
0.92 1.01 1.09 1.23 1.21
hyperfine field (Hf) experienced by Fe3+ ions at B-site is higher than that of A-site values. The black dot shows the experimental data and the solid red coloured curve between the two magnetic sextets represents the best fitted curve of the experimental data of the synthesized samples. These two magnetic sextets found in spectra correspond to two interstitial sites (A-site & B-site) present in the lattice. The internal magnetic field (Hint) arises due to various interactions can be expressed by following equation:
Hint = Hcore + HSTHF + HTHF +
HD
4. Conclusions The silver doped magnesium-manganese nanoferrites are successfully synthesized by sol-gel technique. The XRD patterns confirmed the formation of cubic single phase without any additional impurity peaks. The lattice parameter and x-ray density were observed to increase with the addition of Mn2+ and Ag + ions. FESEM study depicted the cubical nature of the synthesized nanoferrites having uniform distribution. EDS
(10)
where Hcore is the field owing due to polarization of core s-electrons, HSTHF and HTHF are the super transferred and transferred fields respectively and HD is the dipolar field. The isomer shift (δ) is the shifting
Fig. 7. Mössbauer spectra for Mg1-yMnyAgxFe2-xO4 nanoferrites. 6
Physica B: Condensed Matter 569 (2019) 1–7
R. Jasrotia, et al.
Table 7 Mössbauer parameters for Mg1-yMnyAgxFe2-xO4 nanoferrites. Sample
y = 0.1, x = 0.0 y = 0.3, x = 0.2 y = 0.5, x = 0.4
Line Width (mm/s)
Isomer Shift (mm/s)
Quadrupole Splitting (mm/s)
Hyperfine Field ‘Hf’
A
B
A
B
A
B
A
B
0.36 0.43 0.66
0.77 0.67 0.61
0.19 0.18 0.07
0.24 0.22 0.19
0.021 0.087 0.013
0.045 0.018 −0.185
53.55 53.18 51.47
50.58 50.48 47.13
study depicted the desired stoichiometric ratio of the involved ions. FTIR study indicated two absorption peaks in the range of 400–700 cm−1 with the substitution of silver ions. The estimated values of cations distributions suggested that for 0 ≤ x ≤ 0.3, Ag+ ions prefer to occupy A-sites while for x = 0.4, Ag+ ions also occupied B-sites. The magnetic study indicated the strengthening of the exchange interactions for the low concentration of the Ag+ ions. The observed values of magnetization and retentivity suggested the utility of the synthesized nanoferrites for electromagnet applications.
[7] Y. Slimani, H. Güngüneş, M. Nawaz, A. Manikandan, H.S. El Sayed, M.A. Almessiere, H. Sözeri, S.E. Shirsath, I. Ercan, A. Baykal, Ceram. Int. 44 (2018) 14242. [8] M. Nazrul Islam, A.K.M. Akther Hossain, J. Mater. Res. Technol. 8 (2019) 208. [9] M. Singh, A. Dogra, R. Kumar, Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. Atoms 196 (2002) 315. [10] S. Ghosh, P.M.G. Nambissan, R. Bhattacharya, Phys. Lett. 325 (2004) 301. [11] B.S. Chauhan, R. Kumar, K.M. Jadhav, M. Singh, J. Magn. Magn. Mater. 283 (2004) 71. [12] A. Lakshman, P.S.V. Subba Rao, B.P. Rao, K.H. Rao, J. Phys. D Appl. Phys. 38 (2005) 673. [13] S.K. Sharma, R. Kumar, V.V. Siva Kumar, M. Knobel, V.R. Reddy, A. Gupta, M. Singh, Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interact. Mater. Atoms 248 (2006) 37. [14] S. Kumar, Ravi Kumar, S.K. Sharma, V.R. Reddy, A. Banerjee, Alimuddin, Solid State Commun. 142 (2007) 706. [15] Gagan Kumar, J. Shah, R.K. Kotnala, V.P. Singh, M. Dhiman, S.E. Shirsath, M. Shahbuddin, K.M. Batoo, M. Singh, J. Magn. Magn. Mater. 390 (2015) 50. [16] N. Lwin, R. Othman, S. Sreekantan, M.N.A. Fauzi, J. Magn. Magn. Mater. 385 (2015) 433. [17] N. Lwin, M.N.A. Fauzi, S. Sreekantan, R. Othman, Phys. B Condens. Matter 461 (2015) 134. [18] C.F. Zhang, X.C. Zhong, H.Y. Yu, Z.W. Liu, D.C. Zeng, Physica B 404 (2009) 2327. [19] Gagan Kumar, Ritu Rani, Sucheta Sharma, Khalid M. Batoo, M. Singh, Ceram. Int. 39 (2013) 4813. [20] E.F. Bertaut, C. R. Hebd. Seances Acad. Sci. 230 (1950) 213–215. [21] L. Weil, E.F. Bertaut, L. Bochirol, J. Phys. Radium 11 (1950) 208–212. [22] S.S. More, R.H. Kadam, A.B. Kadam, A.R. Shite, D.R. Mane, K.M. Jadhav, J. Alloy. Comp. 502 (2010) 477. [23] P. Porta, F.S. Stone, R.G. Turner, J. Solid State Chem. 11 (1974) 135. [24] H. Furuhashi, M. Inagaki, S. Naka, J. Inorg. Nucl. Chem. 35 (1973) 3009. [25] B.D. Cullity, Elements of X-Ray Diffraction, Addison Wesley, USA, 1956, p. 474. [26] M.H. Khedr, M. Bahgat, W.M.A. El Rouby, Mater. Technol. 23 (2008) 27. [27] Gagan Kumar, R.K. Kotnala, J. Shah, V. Kumar, A. Kumar, P. Dhiman, M. Singh, Phys. Chem. Chem. Phys. 19 (2017) 16669.
Acknowledgement The author V. P. Singh is thankful to Indian agency DRDO for its constant support and funding through the whole research work (Project No. ERIP/PR/1303129/M/01/1564). Authors K.M. Batoo, and S. F. Adil are thankful to the Deanship of Scientific Research at King Saud University for its funding through the Research Group Project No. RG1437-030. References [1] Anjana Sharma, M. Khalid, E.H. Batoo, Raslan S.F. Adil, Gagan Kumar, Vacuum 157 (2018) 422. [2] A. Goldman, Modern Ferrite Technology, Springer Science & Business Media, 2006. [3] S.F. Mansour, M.A. Elkestawy, Ceram. Int. 37 (2011) 1175. [4] M.A. Ahmed, Samiha T. Bishay, S.I. El-dek, G. Omar, J. Alloys Compds. 509 (2011) 7891. [5] V.P. Singh, Himachal Pradesh University, Shimla, India, Ph.D. Thesis (2017). [6] Gagan Kumar, J. Shah, R.K. Kotnala, V.P. Singh, Sarveena, G. Garg, S.E. Shirsath, K.M. Batoo, M. Singh, Mater. Res. Bull. 63 (2015) 216.
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