Temperature-induced magnetization reversal in FeCr2 xAlxS4

In this paper, temperature-induced magnetization reversal in FeCr 2− x Al x S 4 ( x = 0.8, 1.0) is reported. Low-field magnetization measurements indicate that this system displays substantial irreversibility between zero-field-cooling (ZFC) and field-cooling (FC) sequences. Upon warming, the ZFC magnetization is found to change sign twice; however, the FC magnetization changes sign only once. Magnetic hysteresis loop measurements reveal that this system displays a large coercivity at lower temperatures; with increasing temperature, the coercivity decreases abruptly. By accounting for magnetic domain freezing induced by large magnetic anisotropy and domain wall pinning of non-magnetic ions, the multiple sign changes of the magnetization are explained qualitatively.