Using the behavior of the free-energy surface, we compute the irreversibility phase diagram, history-dependent magnetization, and specific heat for three-dimensional diluted antiferromagnets (AF), and random-field Ising ferromagnets (RFIM). Domain-wall hysteresis is studied and found to be qualitatively different for the AF and RFIM. This suggests that impurity pinning plays a dramatic role in the dynamics of the former system. The onset of time-dependent long-range order and magnetization ‘‘anomalies’’ are predicted for certain regions of the phase diagram.

• Received 9 October 1984

DOI:https://doi.org/10.1103/PhysRevB.31.1682