Holmium substituted Samarium iron garnet i.e., Sm3-xHoxFe5O12 (x = 0 and 0.6) were synthesized using solid-state reaction route by sintering at 1400°C for 8 hours. Samples are found to be in single phase form as per XRD patterns and refined by Rietveld refinement technique using Ia-3d space group. The lattice constant is found to be decrease from 12.53Å to 12.43Å with Ho doping. Magnetic hysteresis loops (M-H) are measured at room temperature shows that saturation magnetization is decreases from 21.05 emu/g for x = 0 to 12.06 emu/g for x = 0.6 sample. The anisotropy constant is decreasing from 2.42×105 erg/cc for x = 0 to 1.7×105 erg/cc for x = 0.6 sample. Negative magnetization is observed for x = 0.6 sample which can be explained by using the equation i.e., Mnet = 3MFe(d) – 2MFe(a) + (3-x) MSm + xMHo, where Fe(d) and Fe(a) are the Fe atoms at tetrahedral and octahedral site respectively. The frequency dependence of real part of impedance Z' show a step like behavior which indicates the presence of dielectric relaxation in the samples. The merger of all Z' values at higher frequency is due to release of space charges. - Z'' vs. frequency is also plotted and all the plots show relaxation peaks. With the increase in temperature, the peaks are shifting towards higher frequency which suggests that the relaxation is due to thermally activated charge carriers.
Keywords: Ferrimagnetic, negative magnetization, relaxation behavior.
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