Exchange bias and spin glass states driven by antisite disorder in the double perovskite compound LaSrCoFeO6

Abstract

Antisite (B-site) disorder in double perovskite lattice is responsible for various magnetic phenomena such as exchange bias, spin glass, memory effect, colossal magnetoresistance, etc. By controlling the antisite disorder in the antiferromagnetic double perovskite ${\mathrm{LaSrCoFeO}}_{6}$, we achieve intrinsic exchange bias effect with a large exchange bias field ($\ensuremath{\sim}1.2$ kOe) and giant coercive field ($\ensuremath{\sim}12.8$ kOe). Further, we find that the effect of such antisite disorder induces a spin-glass state in ${\mathrm{LaSrCoFeO}}_{6}$. Multiple signatures of slow dynamics were confirmed by frequency-dependent peak shift, slow spin relaxation, and memory effect over a wide temperature regime ($5\ensuremath{-}80$ K). The AC susceptibility data near the spin-glass temperature ($\ensuremath{\sim}72.1\ifmmode\pm\else\textpm\fi{}0.6$ K) are best fit by a critical slowing down model described by a dynamical exponent $\mathrm{z}\ensuremath{\nu}=7.5\ifmmode\pm\else\textpm\fi{}0.5$ and ${\ensuremath{\tau}}_{0}=1.05\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ s. The origin of exchange bias and spin glass are briefly discussed.