Glassy magnetic behavior induced by $Cu^{2+}$ substitution in frustrated antiferromagnet $ZnCr_2O_4$

Abstract

Structure and magnetic properties of the compounds $Zn_{1-x}Cu_xCr_2O_4$ (ZCCO) are investigated systematically. A structural phase transition from space-group symmetry $Fd3m$ to $I4_1/amd$ is observed in ZCCO. The critical value of the doping, $x$, appears at $0.58\sim 0.62$ through the appearance of a splitting of diffraction peaks at room temperature. Measurements of dc magnetization, ac susceptibility, memory effect and exchange bias-like (EB-like) effect have been performed to reveal the glassy magnetic behaviors of ZCCO. The system with $x\leqslant 0.50$ is suggested as a spin glass-like (SG-like) of magnetic characterization whereas doping values of $0.58\leqslant x\leqslant 0.90$ defines the system as a $"$cluster glass-like$"$ (CG-like) with unidirectional anisotropy. The Cu content suppresses the geometrical frustration of $ZnCr_2O_4$, which may correlate with the pinning effect of Cu sublattice on Cr sublattice to a preferential direction.