Standing spin wave mode in RFIM: Patterns and athermal nonequilibrium phases

The dynamical responses of random field Ising model at zero temperature, driven by standing magnetic field wave, are studied by Monte Carlo simulation in two dimensions. The three different kinds of distribution of quenched random field are used here, uniform, bimodal and Gaussian. In all cases, three distinct dynamical phases were observed, namely, the pinned, structured and random. In the pinned phase no spin flip is observed. In the structured phase standing spin wave modes are observed. The random phase is shown with no observed regular pattern. For a fixed value of the amplitude of the standing magnetic field wave, in the region of small quenched field, the system remains in a pinned phase. In the intermediate range of values of random field, a standing spin wave mode (structured phase) is observed. The regular pattern of this spin wave mode disappears for higher values of random field yielding a random phase. The comprehensive phase boundaries are drawn in all three cases. The boundary of pinned phase is analytically calculated for uniform and bimodal types of quenched random fields.