A Monte Carlo study of the specific heat of diluted antiferromagnets

The three-dimensional diluted antiferromagnet in a magnetic field has a lon ge-range ordered state for sufficiently low temperatures and external field s. We study the irreversibilities at the phase transition from this state i nto the paramagnetic state at higher temperatures. Performing field cooling and zero field cooling simulation procedures we find a small irreversibili ty in the internal energy and the specific heat, although the behavior of t he order parameter is irreversible and the phase transition is suppressed i n the FC case. The specific heat shows a noncritical broad maximum above th e transition temperature T-c. The results are compatible with recent experi mental results obtained by Satooka et al., whereas our interpretation of th e data is different.