RESPONSE OF A KINETIC ISING SYSTEM TO OSCILLATING EXTERNAL FIELDS - AMPLITUDE AND FREQUENCY-DEPENDENCE

The S=1/2, nearest-neighbor, kinetic Ising model has been used to mode l magnetization switching in nanoscale ferromagnets. For this model, e arlier work based on the droplet theory of the decay of metastable pha ses and Monte Carlo simulations has shown the existence of a size depe ndent spinodal field which separates deterministic and stochastic deca y regimes. We extend the above work to study the effects of an oscilla ting field on the magnetization response of the kinetic Ising model. W e compute the power spectral density of the time-dependent magnetizati on for different values of the amplitude and frequency of the external field, using Monte Carlo simulation data. We also investigate the amp litude and frequency dependence of the probability distributions for t he hysteresis loop area and the period-averaged magnetization. The tim e-dependent response of the system is classified by analyzing the beha vior of these quantities within the framework of the distinct determin istic and stochastic decay modes mentioned above. (C) 1996 American In stitute of Physics.