Random local anisotropy in spin glasses

Field-cooled Au82.5{Fe}17.5$ in a large demagnetization configuration shows a very pronounced decrease of the magnetization below 50 K, while on field heating, a steep increase of the magnetization follows above 50 K. This behavior is explained by a previously proposed model involving the effect of quasirandom local anisotropy on magnetic cluster moments, which is overcome at {~}50 K by thermal activation. The time-dependent, viscous reorientation of the cluster moments also needs to be taken into consideration.