Irreversibility in diluted antiferromagnets

Abstract

We compute the irreversibility phase diagram, and history-dependent magnetizations for diluted Ising antiferromagnets in three dimensions. We use an iterative mean-field technique which has proved quite successful for treating spin glasses. Motion of the domain walls as the magnetic field is varied at low temperature is also discussed. The onset of time-dependent long-range order and magnetization anomalies are predicted for certain regions of the H-T phase diagram from our studies of the free-energy surface. Our results are compared to those of the random field ferromagnet and spin glasses, which have the common feature that on the time scale of a physical measurement the system is trapped in a local minimum of the free-energy surface. Irreversibility then results primarily from the disappearance of a given minimum as the field or temperature are changed and not from tunneling or thermal activation processes.