Hysteresis in (formula presented) ising square lattices

The magnetic hysteresis of (Formula presented) Ising lattices is analyzed performing a zero-temperature random-walk minimizing energy. A steplike structure presenting a loop divided in four sections is observed. It is shown by Monte Carlo calculations that this structure is rounded off as temperature increases until a thin S shape is obtained, which is in general agreement with experimental results. A simple explanation for this form of hysteresis is given supporting universality and size independence.