  The hysteresis of the Ising model in a spatially homogeneous AC field is
studied using both mean-field calculations and two-dimensional Monte Carlo
simulations. The frequency dispersion and the temperature dependence of the
hysteresis loop area are studied in relation to the dynamic symmetry loss. The
dynamic mechanisms may be different when the hysteresis loops are symmetric or
asymmetric, and they can lead to a double-peak frequency dispersion and
qualitatively different temperature dependence.
