Structure and magnetic properties evolution of nickel–zinc ferrite with lanthanum substitution

Journal of Magnetism and Magnetic Materials 379 (2015) 232–238

Contents lists available at ScienceDirect

Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm

Structure and magnetic properties evolution of nickel–zinc ferrite with lanthanum substitution Xuehang Wu a, Wenwei Wu a,b,n, Liqin Qin a, Kaituo Wang a, Shiqian Ou a, Kaiwen Zhou c, Yanjin Fan d a

School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, PR China Guangxi Colleges and Universities Key Laboratory of Applied Chemistry Technology and Resource Development, Nanning 530004, PR China c School of Materials Science and Engineering, Guangxi University, Nanning 530004, PR China d Guangxi Institute of Metallurgy, Nanning 530023, PR China b

art ic l e i nf o

a b s t r a c t

Article history: Received 17 August 2014 Received in revised form 9 December 2014 Accepted 18 December 2014 Available online 19 December 2014

La3 þ -doped Ni–Zn ferrites with a nominal composition of Ni0.5Zn0.5LaxFe2–xO4 (where x ¼0–0.3) are prepared by solid-state reaction at low temperatures. X-ray diffraction data shows that single phase Ni0.5Zn0.5Fe2O4 is obtained at 600 °C, but all samples consist of the main spinel phase in combination of a small amount of a foreign LaFeO3 phase after doping. When the precursor is calcined at 900 °C, the lattice constants of the ferrites initially increase after La3 þ doping, but then become smaller with additional La3 þ doping. The addition of La3 þ results in a reduction of crystallite size. Magnetic measurement reveals that the specific saturation magnetization (Ms) of the as-prepared ferrites decreases with increasing La3 þ substitution, while the coercivity (Hc) of Ni0.5Zn0.5LaxFe2–xO4 obtained above 800 °C increases with increasing La3 þ substitution. & 2014 Published by Elsevier B.V.

Keywords: Ferrite Magnetic properties Chemical synthesis Structure evolution

1. Introduction Spinel ferrites M2 þ Fe2O4 (M2 þ ¼Cu2 þ , Mn2 þ , Mg2 þ , Zn2 þ , Ni , Co2 þ , etc.) are a technologically important group of materials owing to their diverse applications in high-density magnetic recording, ferrofluids technology, biomedical drug delivery, catalysis, energy storage, gas sensors, and magnetic resonance imaging (MRI) [1–14]. Within this group, Ni–Zn ferrites is a kind of very important soft magnetic material. Ni–Zn ferrites have many advantages, such as low cost, high resistivity, mechanical hardness, high Curie temperature, and chemical stability. So, Ni–Zn ferrites are attractive for microwave device applications and other relevant fields. Therefore, Ni–Zn ferrites are always the focus of research. Compared to other composition Ni–Zn ferrites, Ni0.5Zn0.5Fe2O4 has higher specific saturation magnetizations [5]. Ni–Zn ferrites properties were highly dependent on the composition, synthesis methods, and doped elements. Rare earth oxides are good electrical insulators with high electrical resistivity. The occupation of rare earth ions on ‘B’ sites impedes the motion of Fe2 þ in the conduction process, thus causing an increase in resistivity [1]. Doped rare earth in ferrites was considered to be an 2þ

n Corresponding author at: School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, PR China. Fax: þ 86 771 3233718. E-mail address: [email protected] (W. Wu).

http://dx.doi.org/10.1016/j.jmmm.2014.12.057 0304-8853/& 2014 Published by Elsevier B.V.

effective means to improve the performance of ferrites [1,15–22]. Various synthetic approaches have been pursued to prepare spinel Ni1–xZnxFe2O4 and doped Ni1–xZnxFe2O4 with different particle sizes and morphological features, including ceramic technique [17,23], solid-state reaction at low temperatures [5,24], hydrothermal method [25,26], co-precipitation method [15,27,28], citrate precursor method [29,30], high energy ball milling method [31], sol–gel synthesis [16,18,32], self-combustion method [33], molten salt method [34], refluxing method [35], reverse micelle method [36,37], solvothermal method [38], flash combustion technique [39], and chitosan method [40]. In the synthesis of Ni0.5Zn0.5Fe2O4, the crystallite diameter, morphology, and crystalline phases of Ni0.5Zn0.5Fe2O4 associated with its performances highly depend on the synthesis method and calcination temperature. Dey et al. [31] synthesized nanosized Ni0.5Zn0.5Fe2O4 by the high energy ball milling method. The value of specific saturation magnetization at 27 °C is 30.7 emu/g. The sample does not show any detectable hysteresis at 27 °C, indicating superparamagnetic behavior of Ni0.5Zn0.5Fe2O4. Gao et al. [32] obtained irregular polyhedrons Zn0.5Ni0.5Fe2O4 with a size of 29 nm by the sol–gel method, followed by calcination at 900 °C. The values of specific saturation magnetization and coercivity at room temperature are 53 emu/g and 40 Oe, respectively. Peng et al. [17] prepared Pr3 þ -doped Ni–Zn ferrites with a nominal composition of Ni0.5Zn0.5PrxFe2–xO4 (x¼0–0.08) by the ceramic technique. The results showed that the specific saturation magnetization (Ms) of

2. Experimental

233

100

0.00

96

-0.05

92

-0.10

88 84

-0.15

80

-0.20

76 72

-0.25

75.7 C

150

DTG (mg/min)

the as-prepared ferrites decreased, while the coercivity (Hc) increased with increasing Pr3 þ substitution. Although many researchers have made great efforts to obtain high-performance Ni– Zn ferrites and/or doped rare earth ferrites, facile and scalable synthesis of Ni–Zn ferrites at a low cost is still a significant challenge. This study aims to prepare Ni0.5Zn0.5LaxFe2–xO4 by calcining carbonates precursor in air and study structure and magnetic properties evolution of Ni0.5Zn0.5LaxFe2–xO4. Our results clearly show that the magnetic properties, in particular the specific magnetizations (Ms) and coercivity (Hc), can be precisely tailored by controlling the composition as well as the calcination temperature.

TG (%)

X. Wu et al. / Journal of Magnetism and Magnetic Materials 379 (2015) 232–238

300 450 600 Temperature ( C)

750

Fig. 1. TG/DTG curves of Ni0.5Zn0.5CO3–Fe2O3∙1.7H2O, at a heating rate of 10 °C min  1 in air.

2.1. Reagent and apparatus All chemicals used are of reagent-grade purity (purity 499.9%). The TG measurement was conducted using a Netzsch Sta 409 PC/ PG thermogravimetric analyzer under continuous flow of air (40 mL min  1). The sample mass was approximately 12 mg. X-ray powder diffraction (XRD) was performed using a Rigaku D/Max 2500V diffractometer equipped with a graphite monochromator and a Cu target. The radiation applied was Cu Kα (λ ¼0.15406 nm), operated at 40 kV and 50 mA. The XRD scans were conducted from 5° to 70° in 2θ, with a step size of 0.02°. The morphologies of the synthesis products were observed using a S-3400 scanning electron microscope (SEM). The specific magnetization (M) of the calcined sample powders were carried out at room temperature using a vibrating sample magnetometer (Lake Shore 7410). 2.2. Preparation of Ni0.5Zn0.5LaxFe2–xO4 The Ni0.5Zn0.5LaxFe2–xO4 (x¼ 0, 0.1, 0.2, and 0.3) precursor samples were prepared by solid-state reaction at low temperatures [24] using NiSO4  7H2O, ZnSO4  7H2O, FeSO4  7H2O, La(NO3)3  6H2O, and Na2CO3  10H2O as raw materials. In a typical synthesis, NiSO4  7H2O (8.86 g), ZnSO4  7H2O (9.07 g), FeSO4  7H2O (35.08 g), Na2CO3  10H2O (62.28 g), and surfactant polyethylene glycol-400 (3.0 mL, 50 vol%) were placed in a mortar, and the mixture was thoroughly ground by hand with a rubbing mallet for 35 min. The strength applied was moderate. The reactant mixture gradually became damp, and a paste was formed immediately. The reaction mixture was kept at 30 °C for 1.5 h. The mixture was washed with deionized water to remove soluble inorganic salts until SO42  ion cannot be visually detected with a 0.5 mol L  1 BaCl2 solution. The solid was then washed with a small amount of anhydrous ethanol. A red-brown solid was obtained after dried at 80 °C in air for 4 h, implying that Fe2 þ in the precipitate was oxidized into Fe3 þ . The resulting material was determined to be Ni0.5Zn0.5CO3–Fe2O3∙1.7H2O. A similar synthetic procedure was used to synthesize other Ni0.5Zn0.5LaxFe2–xO4 precursor. A high-crystallized Ni0.5Zn0.5LaxFe2–xO4 was obtained when the precursor was calcined over 600 °C for 3 h in a muffle furnace.

defined steps. The first step started at about 54 °C and ended at 114.7 °C, which can be attributed to the dehydration of the 1.7 waters from Ni0.5Zn0.5CO3–Fe2O3∙1.7H2O (mass loss: observed, 9.80%; theoretical, 9.81%). The second transformation step started at 114.7 °C and ended at 400 °C, attributed to the thermal decomposition of Ni0.5Zn0.5CO3–Fe2O3 into Ni0.5Zn0.5Fe2O4 and the one CO2 molecule (mass loss: observed, 14.9%; theoretical, 14.09%). 3.2. XRD analyses of the precursor and the calcined products Fig. 2 shows the XRD patterns of calcined samples from different calcination temperatures for 3 h. Fig. 2a shows that when Ni0.5Zn0.5CO3–Fe2O3∙1.7H2O was calcined at 600 °C for 3 h, a diffraction pattern with strong intensity and smoothed baseline was observed. The calcined product therefore has a high degree of crystallinity. All the diffraction peaks in the pattern agreed with those of cubic Ni0.5Zn0.5Fe2O4 with space group Fd-3m (227) from PDF card 52-0278. Fig. 2b–d shows the XRD patterns of Ni0.5Zn0.5LaxFe2–xO4 (x¼ 0.1, 0.2, and 0.3) from different calcination temperatures for 3 h. The results showed that all samples consisted of the main spinel phase in combination of a small amount of a foreign LaFeO3 phase after doping. Similar phenomenon was also observed for La3 þ -doped ferrites [1,18,20,41]. Compared with solid-state reaction at high temperature using a mixture of oxides, the crystallization temperature of Ni0.5Zn0.5LaxFe2–xO4 in our paper is lower, and higher degree of crystallinity of Ni0.5Zn0.5LaxFe2–xO4. The reason is that direct high temperature solid-state reaction exists difficult penetration between the solid particles, resulting in crystallization of Ni0.5Zn0.5LaxFe2–xO4 at a higher temperature, and a lower degree of crystallinity. However, in our study, a mixture of NiSO4  7H2O, ZnSO4  7H2O, FeSO4  7H2O, La(NO3)3  6H2O, and Na2CO3  10H2O was grinded at room temperature, precursor carbonates can be obtained with molecular-level scale and the uniform mixing at first, crystalline Ni0.5Zn0.5LaxFe2–xO4 can be obtained at lower temperature when the precursor was calcined in air. The crystallite diameter of Ni0.5Zn0.5LaxFe2–xO4 was estimated using the following Scherrer formula [42]:

3. Results and discussion

D = K λ/(β cos θ),

3.1. TG/DTG analysis of Ni0.5Zn0.5CO3–Fe2O3∙1.7H2O

where D is the crystallite diameter, K ¼ 0.89 (the Scherrer constant), λ ¼0.15406 nm (wavelength of the X-ray used), β is the width of line at the half-maximum intensity, and θ is the corresponding angle. The crystallite sizes of Ni0.5Zn0.5LaxFe2–xO4 from calcining the precursor at 600 °C, 700 °C, 800 °C, and 900 °C are shown in Fig. 3. The crystallite size of Ni0.5Zn0.5LaxFe2–xO4

Fig. 1 shows the TG/DTG curves of the precursor at a heating rate of 10 °C min  1, from ambient temperature to 800 °C. The TG/ DTG curves show that the thermal transformation of Ni0.5Zn0.5CO3–Fe2O3∙1.7H2O below 800 °C occurred in two well-

(1)

234

X. Wu et al. / Journal of Magnetism and Magnetic Materials 379 (2015) 232–238

Fig. 2. XRD patterns of Ni0.5Zn0.5LaxFe2–xO4 at different temperatures for 3 h: (a) Ni0.5Zn0.5Fe2O4, (b) Ni0.5Zn0.5La0.1Fe1.9O4, (c) Ni0.5Zn0.5La0.2Fe1.8O4, and (d) Ni0.5Zn0.5La0.3Fe1.7O4.

Table 1 The lattice constants of Ni0.5Zn0.5LaxFe2–xO4 obtained at different temperatures. Composition

Ni0.5Zn0.5Fe2O4 Ni0.5Zn0.5La0.1Fe1.9O4 Ni0.5Zn0.5La0.2Fe1.8O4 Ni0.5Zn0.5La0.3Fe1.7O4

Fig. 3. Crystallite diameters of Ni0.5Zn0.5LaxFe2–xO4, obtained at different temperatures in air for 3 h.

increases with the increase of the calcination temperature except Ni0.5Zn0.5La0.3Fe1.7O4 obtained at 600 °C; The crystallite size of Ni0.5Zn0.5LaxFe2–xO4 decreases with increasing La3 þ substitution between 700 and 800 °C. The crystallinity of Ni0.5Zn0.5Fe2O4 can be calculated by MDI Jade 5.0 software. The crystallinities of Ni0.5Zn0.5Fe2O4 obtained at 600 °C, 700 °C, 800 °C, and 900 °C were 99.03%, 99.99%, 100%, and 100%, respectively.

Lattice constant (Å) 600 °C

700 °C

800 °C

900 °C

8.38298 8.38306 8.38285 8.38280

8.38281 8.38268 8.38276 8.38272

8.38292 8.38286 8.38286 8.38291

8.38286 8.38289 8.38270 8.38295

The lattice constants, a, of the as-prepared samples calculated from the XRD data are listed in Table 1. When Ni0.5Zn0.5LaxFe2–xO4 precursor was calcined at 900 °C, the lattice constant raised after the addition of small amount of La3 þ ions (x¼ 0.1) at first, then dropped down when the doping amount of La3 þ ions increased to x¼ 0.2. However, the lattice constant raised after the doping amount of La3 þ ions was x ¼0.3. The initial increase in lattice constant of the as-prepared ferrite samples can be explained on the basis of the radii of metal ions in the samples. The radius of La3 þ ion (1.061 Å) is larger than that of Fe3 þ ion (0.67 Å). So, the La3 þ ion in the ferrites could behave as other ions from the lanthanide series like Pr, Yb, Er, Dy, Tb, Gd, Sm and Ce locating in the B-sublattice with adequate space. The replacement of Fe3 þ ions in octahedral B sites by La3 þ ions would cause the expansion of unit cell, resulting in larger lattice constants [17,18,43]. However, with additional La3 þ doping, the lattice constants decreased. This can be attributed to that part of La3 þ ions could not enter the

X. Wu et al. / Journal of Magnetism and Magnetic Materials 379 (2015) 232–238

235

Fig. 4. SEM images of the products synthesized at different temperatures for 2 h: (a) Ni0.5Zn0.5Fe2O4–700 °C, (b) Ni0.5Zn0.5Fe2O4–800 °C, (c) Ni0.5Zn0.5La0.1Fe1.9O4–800 °C, (d) Ni0.5Zn0.5La0.2Fe1.8O4–800oC, and (e) Ni0.5Zn0.5La0.3Fe1.7O4–800 °C.

octahedral site but form a second phase LaFeO3, thereby causing the lattice contraction and thus the decrease in lattice constant. When the amount of La3 þ increased to x ¼0.3, the lattice parameters increase due to the significant increase of amount of the second phase LaFeO3. Similar phenomenon was also observed for La3 þ -doped Ni–Zn ferrites obtained by a sol–gel auto-combustion method [18]. 3.3. SEM analyses of the calcined samples The morphologies of the calcined samples are shown in Fig. 4. Fig. 4a shows that the Ni0.5Zn0.5Fe2O4 sample obtained at 700 °C is composed of approximately spherical particles, and particles sizes are between 50 and 100 nm. The calcined sample at 800 °C keeps

approximately spherical morphology, and the particle sizes are mainly 100 nm (Fig. 4b). Fig. 4c–e shows SEM images of the Ni0.5Zn0.5LaxFe2–xO4 (x ¼0.1, 0.2, and 0.3) samples obtained at 800 °C, respectively. The Ni0.5Zn0.5LaxFe2–xO4 sample at 800 °C is also composed of approximately spherical morphology, and the particle sizes are mainly between 50 and 150 nm. The average crystallite sizes of the calcined samples determined by X-ray diffraction are significantly smaller than the values determined by SEM. This difference can be attributed to the fact that the values observed by SEM have the size of the secondary particles, which are composed of several or many crystallites by soft reunion. In addition, the X-ray line broadening analysis discloses only the size of a single crystallite.

236

X. Wu et al. / Journal of Magnetism and Magnetic Materials 379 (2015) 232–238

Fig. 5. M–H (magnetization–hysteresis) loops of Ni0.5Zn0.5LaxFe2–xO4 samples obtained at different temperatures for 3 h.

70

x=0 x=0.1 x=0.2 x=0.3

Ms (emu/g)

60 50 40 30 20 600

650

700

750

800

850

900

o

Temperature ( C) Fig. 6. Dependence of the specific saturation, magnetization on calcination temperature.

3.4. Magnetic properties of Ni0.5Zn0.5LaxFe2–xO4 The hysteresis loops of Ni0.5Zn0.5LaxFe2–xO4 samples calcined at different temperatures are shown in Fig. 5. Fig. 6 shows dependence of specific saturation magnetization on calcination temperature. Among Ni0.5Zn0.5LaxFe2–xO4 (x¼ 0, 0.1, 0.2, and 0.3), Ni0.5Zn0.5Fe2O4 obtained at 900 °C has the largest specific saturation magnetization value, 70.13 emu/g. Compared to magnetic properties of NiFe2O4 [44] and ZnFe2O4 [45] obtained at same temperature, the Ni0.5Zn0.5Fe2O4 exhibits higher specific saturation magnetizations than NiFe2O4 and ZnFe2O4, which implies that Ni2 þ and Zn2 þ ions in Ni0.5Zn0.5Fe2O4 have a synergistic effect in

improving the specific saturation magnetization of Ni0.5Zn0.5Fe2O4. However, specific saturation magnetization decreases with the increase of La3 þ content in Ni0.5Zn0.5LaxFe2–xO4. Dependences of remanence (Mr) and coercivity (Hc) on calcination temperature are shown in Fig. 7a and b, respectively. Among Ni0.5Zn0.5LaxFe2–xO4, Ni0.5Zn0.5La0.1Fe1.9O4 obtained at 700 °C has the largest remanence value, 10.13 emu/g (Fig. 7a). Compared to other composition Ni0.5Zn0.5LaxFe2–xO4 at different calcination temperature, Ni0.5Zn0.5La0.3Fe1.7O4 obtained at 800 °C has the largest coercivity value, 120.09 Oe (Fig. 7b). In comparison with Ni– Zn ferrites and/or rare earth-doped Ni–Zn ferrites, Ni0.5Zn0.5LaxFe2–xO4 prepared by solid-state reaction at low temperatures has the prominent advantages of lower calcination temperature, larger coercivity, and higher specific saturation magnetization value, as summarized in Table 2.

4. Conclusions We have successfully synthesized Ni0.5Zn0.5LaxFe2–xO4 (x¼ 0, 0.1, 0.2, and 0.3) by calcining carbonates precursor in air. The XRD analysis suggests that a cubic Ni0.5Zn0.5Fe2O4 with space group Fd3m (227) can be obtained by calcining Ni0.5Zn0.5CO3–Fe2O3∙1.7H2O over 600 °C in air for 3 h. Single phase Ni0.5Zn0.5Fe2O4 can be obtained at lower temperature, attributed to the formation of precursor carbonates with molecular-level scale and uniform mixing from solid-state reaction at low temperatures. Magnetic characterization indicates that magnetic properties of Ni0.5Zn0.5LaxFe2–xO4 depend on the composition and calcination temperature. La3 þ ions in Ni0.5Zn0.5La0.3Fe1.7O4 can improve the coercivity of Ni0.5Zn0.5La0.3Fe1.7O4; Ni0.5Zn0.5La0.3Fe1.7O4 obtained

X. Wu et al. / Journal of Magnetism and Magnetic Materials 379 (2015) 232–238

237

Fig. 7. Dependence of remanence (Mr) and coercivity (Hc) on calcination temperature.

Table 2 Comparison of different rare earth-doped ferrites. Composition

Synthesis method

Calcination temperature (oC)

Ms (emu/g)

Hc (Oe)

References

Ni0.5Zn0.5Fe2O4 Ni0.4Zn0.5La0.1Fe2O4 Ni0.5Zn0.4Mg0.1La0.01Fe1.99O4 Ni0.5Zn0.5Fe1.92Pr0.08O4 Ni0.5Zn0.5Fe2O4 Ni0.8Zn0.2Fe1.98Dy0.02O4 Ni0.5Zn0.5Fe2O4 Ni0.5Zn0.5La0.1Fe2O4 Ni0.5Zn0.5La0.1Fe1.9O4

Coprecipitation Coprecipitation Sol–gel Ceramic technique Mechanical alloying Sol–gel method

700 700 850 1175 1000 900 900 800 700

45.3 32.8 63 66.23 13.67 59 70.13 48.65 41.9

70.2 50.5

[15] [15] [16] [17] [46] [47] This work This work This work

at 800 °C has the largest coercivity value, 120.09 Oe. Our strategy is simple but very effective for Ni0.5Zn0.5LaxFe2–xO4 synthesis, which is also applicable to mass production for other ferrites and/or rare earth-doped ferrites.

Acknowledgements This study was financially supported by the National Natural Science Foundation of China (Grant no. 21161002) and the Guangxi University Student Innovation Foundation of China (Grant no. 1301056).

References [1] E.E. Ateia, M.A. Ahmed, L.M. Salah, A.A. El-Gamal, Effect of rare earth oxides and La3 þ ion concentration on some properties of Ni–Zn ferrites, Physica B 445 (2014) 60–67. [2] M.S. Anwar, F. Ahmed, B.H. Koo, Enhanced relative cooling power of Ni1– xZnxFe2O4 (0.0 r xr 0.7) ferrites, Acta Mater. 71 (2014) 100–107. [3] W.W. Wu, J.C. Cai, X.H. Wu, S. Liao, A.G. Huang, Co0.35Mn0.65Fe2O4 magnetic particles: preparation and kinetics research of thermal process of the precursor, Powder Technol. 215– 216 (2012) 200–205. [4] A. Ghasemi, M. Mousavinia, Structural and magnetic evaluation of substituted NiZnFe2O4 particles synthesized by conventional sol–gel method, Ceram. Int. 40 (2014) 2825–2834. [5] W.W. Wu, Y.N. Li, K.W. Zhou, X.H. Wu, S. Liao, Q. Wang, Nanocrystalline Zn0.5Ni0.5Fe2O4: preparation and kinetics of thermal process of precursor, J. Therm. Anal. Calorim. 110 (2012) 1143–1151. [6] J.W. Huang, P. Su, W.W. Wu, Y.N. Li, X.H. Wu, S. Liao, Preparation of magnetic Cu0.5Mg0.5Fe2O4 nanoparticles and kinetics of thermal process of precursor, J. Supercond. Novel Magn. 25 (2012) 1971–1977. [7] L.Q. Qin, M.L. Gao, W.W. Wu, S.Q. Ou, K.T. Wang, B. Liu, X.H. Wu, Co1– xMgxFe2O4 magnetic particles: preparation and kinetics research of thermal transformation of the precursor, Ceram. Int. 40 (2014) 10857–10866. [8] K.W. Zhou, W.W. Wu, Y.N. Li, X.H. Wu, S. Liao, Preparation of magnetic nanocrystalline Mn0.5Mg0.5Fe2O4 and kinetics of thermal decomposition of precursor, J. Therm. Anal. Calorim. 114 (2013) 205–212.

4.35 50 67 38.41 98.46 56.2

[9] X.H. Wu, W.W. Wu, K.W. Zhou, L.Q. Qin, S. Liao, Y.J. Lin, Magnetic nanocrystalline Mg0.5Zn0.5Fe2O4: preparation, morphology evolution, and kinetics of thermal decomposition of precursor, J. Supercond. Novel Magn. 27 (2014) 511–518. [10] M. Sajjia, M. Oubaha, M. Hasanuzzaman, A.G. Olabi, Developments of cobalt ferrite nanoparticles prepared by the sol–gel process, Ceram. Int. 40 (2014) 1147–1154. [11] M. Atif, R. Sato Turtelli, R. Grössinger, M. Siddique, M. Nadeem, Effect of Mn substitution on the cation distribution and temperature dependence of magnetic anisotropy constant in Co1  xMnxFe2O4 (0.0r x r0.4) ferrites, Ceram. Int. 40 (2014) 471–478. [12] R. Ali, M.A. Khan, A. Mahmood, A.H. Chughtai, A. Sultan, M. Shahid, M. Ishaq, M.F. Warsi, Structural, magnetic and dielectric behavior of Mg1  xCaxNiyFe2  yO4 nano-ferrites synthesized by the micro-emulsion method, Ceram. Int. 40 (2014) 3841–3846. [13] S. Ramesh, B.C. Sekhar, P.S.V. Subba Rao, B. Parvatheeswara Rao, Microstructural and magnetic behavior of mixed Ni–Zn–Co and Ni–Zn–Mn ferrites, Ceram. Int. 40 (2014) 8729–8735. [14] W. Shen, H.K. Zhu, Y. Jin, H.Q. Zhou, Z.M. Xu, Sintering, microstructure and magnetic properties of low-temperature-fired NiCuZn ferrites doped with B2O3, Ceram. Int. 40 (2014) 9205–9209. [15] Q.L. Lia, Y.F. Wang, C.B. Chang, Study of Cu, Co, Mn and La doped NiZn ferrite nanorods synthesized by the coprecipitation method, J. Alloy. Compd. 505 (2010) 523–526. [16] Y. Liu, S.C. Wei, B.S. Xu, Y.J. Wang, H.L. Tian, H. Tong, Effect of heat treatment on microwave absorption properties of Ni–Zn–Mg–La ferrite nanoparticles, J. Magn. Magn. Mater. 349 (2014) 57–62. [17] Z.J. Peng, X.L. Fu, H.L. Ge, Z.Q. Fu, C.B. Wang, L.H. Qi, H.H. Miao, Effect of Pr3 þ doping on magnetic and dielectric properties of Ni–Zn ferrites by “one-step synthesis”, J. Magn. Magn. Mater. 323 (2011) 2513–2518. [18] X.H. Ren, G.L. Xu, Electromagnetic and microwave absorbing properties of NiCoZn-ferrites doped with La3 þ , J. Magn. Magn. Mater. 354 (2014) 44–48. [19] M. Asif Iqbal, Misbah-ul-Islamn, Irshad Ali, Hasan M. Khan, Ghulam Mustafa, Ihsan Ali, , Study of electrical transport properties of Eu þ 3 substituted MnZnferrites synthesized by co-precipitation technique, Ceram. Int. 39 (2013) 1539–1545. [20] J.W. Huang, P. Su, W.W. Wu, B. Liu, Co0.5Mn0.5LaxFe2  xO4 magnetic particles: preparation and kinetics research of thermal transformation of the precursor, J. Supercond. Novel Magn. 27 (2014) 2317–2326. [21] Z. Karimi, Y. Mohammadifar, H. Shokrollahi, Sh Khameneh Asl, Gh Yousefi, L. Karimi, Magnetic and structural properties of nano sized Dy-doped cobalt ferrite synthesized by co-precipitation, J. Magn. Magn. Mater. 361 (2014) 150–156.

238

X. Wu et al. / Journal of Magnetism and Magnetic Materials 379 (2015) 232–238

[22] L. Kumar, M. Kar, Effect of La3 þ substitution on the structural and magnetocrystalline anisotropy of nanocrystalline cobalt ferrite (CoFe2–xLaxO4), Ceram. Int. 38 (2012) 4771–4782. [23] Y. Liu, J.J. Li, F.F. Min, J.B. Zhu, M.X. Zhang, Microwave-assisted synthesis and magnetic properties of Ni1  xZnxFe2O4 ferrite powder, J. Magn. Magn. Mater. 354 (2014) 295–298. [24] W.W. Wu, J.C. Cai, X.H. Wu, Y.N. Li, S. Liao, Magnetic properties and crystallization kinetics of Zn0.5Ni0.5Fe2O4, Rare Met. 30 (2011) 621–626. [25] C.P. Wang, Y.H. Shen, X.F. Wang, H. Zhang, A.J. Xie, Synthesis of novel NiZnferrite/polyaniline nanocomposites and their microwave absorption properties, Mater. Sci. Semicond. Process. 16 (2013) 77–82. [26] C. Upadhyay, D. Mishra, H.C. Verma, S. Anand, R.P. Das, Effect of preparation conditions on formation of nanophase Ni–Zn ferrites through hydrothermal technique, J. Magn. Magn. Mater. 260 (2003) 188–194. [27] T.J. Shinde, A.B. Gadkari, P.N. Vasambekar, Magnetic properties and cation distribution study of nanocrystalline Ni–Zn ferrites, J. Magn. Magn. Mater. 333 (2013) 152–155. [28] D. Varshney, K. Verma, Substitutional effect on structural and dielectric properties of Ni1  xAxFe2O4 (A ¼Mg, Zn) mixed spinel ferrites, Mater. Chem. Phys. 140 (2013) 412–418. [29] C.T. Jiang, R.J. Liu, X.Q. Shen, L. Zhu, F.Z. Song, Ni0.5Zn0.5Fe2O4 nanoparticles and their magnetic properties and adsorption of bovine serum albumin, Powder Technol. 211 (2011) 90–94. [30] S. Sharma, K. Verma, U. Chaubey, V. Singh, B.R. Mehta, Influence of Zn substitution on structural, microstructural and dielectric properties of nanocrystalline nickel ferrites, Mater. Sci. Eng. B 167 (2010) 187–192. [31] S. Dey, S.K. Dey, B. Ghosh, V.R. Reddy, S. Kumar, Structural, microstructural, magnetic and hyperfine characterization of nanosized Ni0.5Zn0.5Fe2O4 synthesized by high energy ball-milling method, Mater. Chem. Phys. 138 (2013) 833–842. [32] P.Z. Gao, X. Hua, V. Degirmenci, D. Rooney, M. Khraisheh, R. Pollard, R. M. Bowmand, E.V. Rebrov, Structural and magnetic properties of Ni1– xZnxFe2O4 (x ¼0, 0.5 and 1) nanopowders prepared by sol–gel method, J. Magn. Magn. Mater. 348 (2013) 44–50. [33] V.D. Sudheesh, J. Nehra, A. Vinesh, V. Sebastian, N. Lakshmi, D.P. Dutta, V. R. Reddy, K. Venugopalan, Ajay Gupta, Investigation of structural and magnetic properties of Ni0.5Zn0.5Fe2O4 nano powders prepared by self combustion method, Mater. Res. Bull. 48 (2013) 698–704. [34] S. Hallynck, G. Pourroy, S. Vilminot, P.M. Jacquart, D. Autissier, N. Vukadinovic, H. Pascard, Synthesis of high aspect ratio of Ni0.5Zn0.5Fe2O4 platelets for electromagnetic devices, Solid State Sci. 8 (2006) 24–30.

[35] Z.F. Zhong, Q. Li, Y.L. Zhang, H.S. Zhong, M. Cheng, Y. Zhang, Synthesis of nanocrystalline Ni–Zn ferrite powders by refluxing method, Powder Technol. 155 (2005) 193–195. [36] V. Uskoković, M. Drofenik, I. Ban, The characterization of nanosized nickel– zinc ferrites synthesized within reverse micelles of CTAB/1–hexanol/water microemulsion, J. Magn. Magn. Mater. 284 (2004) 294–302. [37] S. Gubbala, H. Nathani, K. Koizol, R.D.K. Misra, Magnetic properties of nanocrystalline Ni–Zn, Zn–Mn, and Ni–Mn ferrites synthesized by reverse micelle technique, Physica B 348 (2004) 317–328. [38] W. Yan, W. Jiang, Q.H. Zhang, Y.G. Li, H.Z. Wang, Structure and magnetic properties of nickel–zinc ferrite microspheres synthesized by solvothermal method, Mater. Sci. Eng. B 171 (2010) 144–148. [39] R.V. Mangalaraja, S. Thomas Lee, S. Ananthakumar, P. Manohard, C.P. Camurri, Effect of composition on initial permeability of Ni1  xZnxFe2O4 prepared by flash combustion technique, Mater. Sci. Eng. A 476 (2008) 234–239. [40] M.A. Gabal, S. Kosa, T.S. Al Mutairi, Structural and magnetic properties of Ni1  xZnxFe2O4 nano-crystalline ferrites prepared via novel chitosan method, J. Mol. Struct. 1063 (2014) 269–273. [41] G. Dascalu, T. Popescu, M. Feder, O.F. Caltun, Structural, electric and magnetic properties of CoFe1.8RE0.2O4 (RE¼ Dy, Gd, La) bulk materials, J. Magn. Magn. Mater. 333 (2013) 69–74. [42] K.T. Wang, X.H. Wu, W.W. Wu, Y.N. Li, S. Liao, Synthesis of perovskite LaCoO3 by thermal decomposition of oxalates: phase evolution and kinetics of the thermal transformation of the precursor, Ceram. Int. 40 (2014) 5997–6004. [43] N. Rezlescu, E. Rezlescu, C. Pasnicu, M.L. Craus, Effects of the rare-earth ions on some properties of a nickel–zinc ferrite, J. Phys.: Condens. Matter 6 (1994) 5707–5716. [44] W.W. Wu, S.Y. Hou, S. Liao, M.J. Wang, X.H. Wu, S.S. Li, Nanocrystalline spinel NiFe2O4 synthesis by solid-state reaction at low heat, Nonferrous Met. 62 (2010) 39–42 (in Chinese). [45] F.S. Li, H.B. Wang, L. Wang, J.B. Wang, Magnetic properties of ZnFe2O4 nanoparticles produced by a low-temperature solid-state reaction method, J. Magn. Magn. Mater. 309 (2007) 295–299. [46] I. Ismail, M. Hashim, S. Kanagesan, I.R. Ibrahim, R. Nazlan, W.N.W.A. Rahman, N.H. Abdullah, F.M. Idris, G. Bahmanrokh, M.S.E. Shafie, M. Manap, Evolving microstructure, magnetic properties and phase transition in a mechanically alloyed Ni0.5Zn0.5Fe2O4 single sample, J. Magn. Magn. Mater. 351 (2014) 16–24. [47] P. Samoila, T. Slatineanu, P. Postolache, A.R. Iordan, M.N. Palamaru, The effect of chelating/combustion agent on catalytic activity and magnetic properties of Dy doped Ni–Zn ferrite, Mater. Chem. Phys. 136 (2012) 241–246.