Hysteresis in +/- J Ising square lattices

The magnetic hysteresis of +/-J Ising lattices is analyzed performing a zer o-temperature random-walk minimizing energy. A steplike structure presentin g a loop divided in four sections is observed, It is shown by Monte Carlo c alculations that this structure is rounded off as temperature increases unt il a thin S shape is obtained, which is in-general agreement with experimen tal results. A simple explanation for this form of hysteresis is given supp orting universality and size independence. [S0163-1829(99)02202-X].