Glassy magnetic behavior induced by Cu2+ substitution in the frustrated antiferromagnet ZnCr2O4

The structure and magnetic properties of the compounds Zn1-xCuxCr2O4 (ZCCO) are investigated systematically. A structural phase transition from space-group symmetry Fd3m to I41/amd is observed in ZCCO. The critical value of the doping, x, appears at 0.58-0.62 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≤0.50 suggests a spin glass-like (SG-like) magnetic characterization whereas doping values of 0.58≤x≤0.90 define the system as 'cluster-glass-like' (CG-like) with unidirectional anisotropy. The Cu content suppresses the geometrical frustration of ZnCr2O4, which may correlate with the pinning effect of the Cu sublattice on the Cr sublattice to a preferential direction