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| Content Provider | IEEE Xplore Digital Library |
|---|---|
| Author | Garimella, M. Kodam, Y. Reddy, V.R. |
| Copyright Year | 2015 |
| Description | Author affiliation: Phys., Indian Inst. of Technol. Madras, Chennai, India (Garimella, M.; Kodam, Y.) || UGC-DAE Consortium for Sci. Res., Indore, India (Reddy, V.R.) |
| Abstract | Nickel ferrite $(NiFe_{2}O_{4}),$ an inverse spinel in which the tetrahedral (A) sites are occupied by $Fe^{3+}$ ions and the octahedral (B) sites are occupied by $Fe^{3+}$ and $Ni^{2+}$ ions, can be represented as $Fe_{A}^{3+}$ $Ni_{B}^{2+}$ $Fe_{B}^{3+}$ $O_{4}^{2-}$ [1-3]. The cation distribution and the resulting magnetic properties are reported to be quite interesting in rare-earth doped nickel ferrite due to the absence of center of symmetry [2, 3]. Kamala Bharathi et al. have reported that, substitution of $Fe^{3+}$ by $Dy^{3+}$ ion in $NiFe_{2}O_{4}$ causes development of magnetocapacitance, leads to ferroelectricity and affects several other properties [3]. These materials play an important role in applications (spintronic memory cell, high frequency devices etc) [4]. There are no reports on thermal behavior of magnetic anisotropy in the rare earth substituted Ni ferrites. Understanding these behaviors will be useful in novel applications such as heat-assisted magnetic recording [4, 5]. In the present work, the temperature dependence of magnetic anisotropy and hyperfine fields of $NiFe_{2-x}Yb_{x}O_{4}$ (x = 0, 0.05, 0.075) are reported. All the samples were prepared by solid state reaction. The materials are found to have formed in inverse spinel structure, from the powder XRD patterns. Rietveld refinement carried out on the XRD patterns revealed that $Yb^{3+}$ ions occupy the B site and the lattice is found to be expanded with the introduction of $Yb^{3+}.$ The lattice constants are 8.3415(1) Å (reported value is 8.34 Å [1]), 8.3436(0) Å and 8.3463(5) Å for x = 0, 0.05 and 0.075 compounds respectively. Magnetization was measured at 5 K, 100 K, 200 K, and 300 K and the magnetization was observed to decrease with x. This is attributed to substitution of $Fe^{3+}$ by $Yb^{3+}$ in the B-site. The saturation magnetization values, at all the measured temperatures obtained through Honda plots are given in Table 1. The moments calculated using Hund's rule (assuming that $Yb^{3+}$ and $Fe^{3+}$ moments are parallel) are 2.82 $μ_{B}/f.u.,$ 2.76 $μ_{B}/f.u.$ and 2.71 $μ_{B}/f.u.$ for x = 0, 0.05 and 0.075 compounds respectively. The experimental values are less in comparison with the calculated moments. In $NiFe_{2}O_{4},$ this difference is in accordance with the reported literature [1-3]. At each temperature, M-H data were fitted to the law of approach to saturation (LAS) [1, 6] and K1(T), the first order magnetocrystalline anisotropy constant at a temperature T, was obtained from LAS. At any given temperature, the observed increase in K1 of x = 0.05 and 0.075 compared with x = 0, is explained on the basis of single-ion model i.e. localized divalent ions in the octahedral site. The temperature dependence of K1 of cubic systems was investigated by plotting ln K1(T) vs ln M(T). The slopes of the straight line obtained are 7.5, 12.5 and 11.44 for x = 0, 0.05 and 0.075 respectively. This can be compared with the value of 10 proposed for magnetic anisotropy in cubic systems [1, 6]. The deviation of the exponent is explained on the extent of localization of the divalent ion. |
| Starting Page | 1 |
| Ending Page | 1 |
| File Size | 424296 |
| Page Count | 1 |
| File Format | |
| e-ISBN | 9781479973224 |
| DOI | 10.1109/INTMAG.2015.7157090 |
| Language | English |
| Publisher | Institute of Electrical and Electronics Engineers, Inc. (IEEE) |
| Publisher Date | 2015-05-11 |
| Publisher Place | China |
| Access Restriction | Subscribed |
| Rights Holder | Institute of Electrical and Electronics Engineers, Inc. (IEEE) |
| Subject Keyword | Ions Compounds Magnetization Anisotropic magnetoresistance Magnetic anisotropy Saturation magnetization Temperature dependence |
| Content Type | Text |
| Resource Type | Article |
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