Monte Carlo simulations of a compressible Ising ferromagnet at constant volume Original Research Article

Compressible Ising models have long been of interest because of the question of how the transition is influenced by elastic degrees of freedom. A careful Monte Carlo study showed, somewhat surprisingly, that an Ising ferromagnet at constant pressure had mean field critical behavior. Subsequently, a theoretical investigation predicted that the effect of elastic interactions depends upon whether the pressure or the volume is held fixed. We have now performed extensive Monte Carlo simulations of a compressible Ising ferromagnet at constant volume and determined the phase diagram as a function of applied magnetic field. In contrast to theoretical predictions, we find a single phase boundary that is first order everywhere except at single point where image. Unusual, slab-like structures are found in the “ordered” phase, and visualization played a crucial role in elucidating the physical behavior.