Temperature dependence of the structural, magnetic, and magnetostrictive properties of zinc-substituted cobalt ferrite

Abstract

This study presents the effects of substitution of Zn 2+ for Co2+ at low concentrations and the effects of temperature variations on the structural, magnetic, and magnetostrictive properties ofcobalt ferrite. Although the Zn-substituted cobalt ferrite samples, Co1−x Zn xFe2O4 (x = 0.02, 0.04, 0.06, 0.09, and 0.17) did not show observable changes in crystal structure, the magnetic and magnetostrictive properties were strongly affected. The variation in magnetic susceptibilitywith composition can be related to the variations in magnetization, coercive field and magnetocrystalline anisotropy. The changes in coercive field were found to be primarily due to the variations in the magnetocrystalline anisotropy. The effect of magnetocrystalline anisotropyon magnetization was stronger at lower cation concentration than at higher concentrations. The decrease in magnetization around 150 K is attributed to the high magnetocrystalline anisotropyat low temperatures which prevented the maximum applied field of 4 MA/m from causing the saturation of magnetization in the samples. Because the magnetocrystalline anisotropy was determined with the magnetization data using the Law of Approach to saturation magnetization, the reliability of the result was found to decrease with decrease in temperature. Peak-to-peakmagnetostriction amplitude and the strain sensitivity decreased with increase in Znsubstitution. KeywordsAmes Laboratory, Zinc, Magnetic anisotropy, Ferrites, Cobalt, Magnetic fields Disciplines Electromagnetics and Photonics CommentsThe following article appeared in Journal of Applied Physics 113 (2013) This study presents the effects of substitution of Zn 2þ for Co 2þ at low concentrations and the effects of temperature variations on the structural, magnetic, and magnetostrictive properties of cobalt ferrite. Although the Zn-substituted cobalt ferrite samples, Co 1Àx Zn x Fe 2 O 4 (x ¼ 0.02, 0.04, 0.06, 0.09, and 0.17) did not show observable changes in crystal structure, the magnetic and magnetostrictive properties were strongly affected. The variation in magnetic susceptibility with composition can be related to the variations in magnetization, coercive field and magnetocrystalline anisotropy. The changes in coercive field were found to be primarily due to the variations in the magnetocrystalline anisotropy. The effect of magnetocrystalline anisotropy on magnetization was stronger at lower cation concentration than at higher concentrations. The decrease in magnetization around 150 K is attributed to the high magnetocrystalline anisotropy at low temperatures which prevented the maximum applied field of 4 MA/m from causing the saturation of magnetization in the samples. Because the magnetocrystalline anisotropy was determined with the magnetization data using the Law of Approach to saturation magnetization, the reliability of the result was found to decrease with decrease in temperature. Peak-to-peak magnetostriction amplitude and the strain sensitivity decreased with increase in Zn substitution. V C 2013 AIP Publ...

Temperature dependence of magnetic properties of heat treated cobalt ferrite

“…) This trend in materials based on cobalt ferrite has been explained on the basis of the competition between the thermal energy and the magnetocrystalline anisotropy energy in response to the applied magnetic field. 14 As temperature decreased from 400 K, the applied magnetic field increasingly became more effective in aligning the magnetic moments in its direction. This results in increased saturation magnetization as seen in regime 1.…”

“…2 which compares the saturation magnetization of the heat treated samples to those of Zn-substituted cobalt ferrite. 14 The mechanism by which heat treatment results in the increase in saturation magnetization is cation redistribution arising due to increased ionic mobility at elevated temperatures. It has been shown that annealing and quenching of cobalt ferrite results in the increased occupancy of Fe 3þ on the octahedral sites.…”

“…10 The trends observed at lower and higher heat treatment temperatures are comparable to those observed in cation substitutions at lower and higher cation concentrations, respectively. 14,18 The effect of cation substitution in reducing the magnetocrystalline anisotropy is stronger at higher concentrations of substituted cations. 18,19 This enables the applied magnetic field to have a greater effect in increasing the magnetization at higher concentrations.…”

“…In general, cation substitution appears to have a stronger effect on magnetocrystalline anisotropy than does heat treatment as deducible by comparing 10 with studies on cation substituted cobalt ferrite. 5,11,12,14 Figure 5 shows the temperature at which the saturation magnetization reached a maximum (regime 2) plotted against the heat treatment temperature. A decreasing trend with heat treatment temperature was observed.…”

Effect of Er doping on the structural and magnetic properties of cobalt-ferrite

“…information storage systems, 1 ferro-fluid technology, 2 magnetic refrigeration, 3 magnetic diagnostics, 4 and magnetostriction. 5 In cobalt-ferrite the presence of doping elements and the thermal history during the synthesis and processing alter the metal ions distribution and hence influence their structural and magnetic properties. 6 The lanthanide series elements/ions have a net magnetic moment that depends upon the number of f-orbital electrons; and among them Er þ3 is relatively small in size (89 pm), and has relatively high magnetic moment (7 l B ).…”