Anomalous Relaxation in the Random-Field Ising Model and Related Systems

Abstract

Anomalous relaxation observed in diluted antiferromagnets in a homogeneous external field at low temperature is explained for real, magnetic systems. For systems with weak crystal-field anisotropy the domain size is controlled by the Bruinsma-Aeppli mechanism and is field dependent, whereas bond randomness is irrelevant. If the anisotropy is strong the walls are pinned by random bonds. Random fields are merely responsible for readjustments of the interface on small scales explaining the relaxation of the magnetization after a decrease in the field.