Cationic redistribution induced spin-glass and cluster-glass states in spinel ferrite

Abstract

The effect of the cationic redistribution on the complex spinel structure and magnetic properties were investigated in ${\mathrm{Zn}}_{0.7}{\mathrm{Cu}}_{0.3}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ ferrite. X-ray photoelectron spectroscopy and x-ray diffraction studies revealed that the system exhibits a mixed spinel structure with ${\mathrm{Fe}}^{3+}, {\mathrm{Zn}}^{2+}$, and ${\mathrm{Cu}}^{2+}$ occupying both tetrahedral and octahedral sublattices. The DC magnetization results revealed the absence of long-range magnetic order in the system. Furthermore, the AC susceptibility data analysis using dynamic scaling laws suggests that the system exhibits magnetic relaxation below two different temperatures: (i) a spin-glass--like transition at low temperature ($\ensuremath{\sim}49.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}$) with critical exponent 10.3 and spin-flip time $\ensuremath{\sim}{10}^{\ensuremath{-}11}\phantom{\rule{0.28em}{0ex}}\mathrm{s}$, and (ii) a cluster-glass--like transition at higher temperature ($\ensuremath{\sim}317\phantom{\rule{0.28em}{0ex}}\mathrm{K}$) with critical exponent 4.6 and spin-flip time $\ensuremath{\sim}{10}^{\ensuremath{-}10}\phantom{\rule{0.28em}{0ex}}\mathrm{s}$. The existence of glassy behavior and magnetic memory effects below the spin-glass transition temperature proves that the system is in nonequilibrium dynamical state. The coexistence of spin-glass and cluster-glass along with the thermal hysteresis between these two transitions could widen the technological applications of these systems.