Kinetic Ising model in an oscillating field: Avrami theory for the hysteretic response and finite-size scaling for the dynamic phase transition

摘要: Hysteresis is studied for a two-dimensional, spin- (1) /(2) , nearest-neighbor, kinetic Ising ferromagnet in sinusoidally oscillating field, using Monte Carlo simulations and analytical theory. Attention focused on large systems moderately strong field amplitudes at temperature below T{sub c}. In this parameter regime, the magnetization switches through random nucleation subsequent growth of {ital many} droplets spins aligned with applied field. Using time-dependent extension Kolmogorov-Johnson-Mehl-Avrami theory metastable decay, we analyze statistical properties hysteresis-loop area correlation between This analysis enables us to accurately predict results extensive simulations. The average loop exhibits an extremely slow approach asymptotic, logarithmic dependence product amplitude frequency. may explain inconsistent exponent estimates reported previous attempts fit experimental numerical data low-frequency behavior quantity power law. At higher frequencies observe dynamic phase transition. Applying standard finite-size scaling techniques from second-order equilibrium transitions nonequilibrium} transition, obtain transition frequency critical exponentsmore » ({beta}/{nu}{approx}0.11,thinsp{gamma}/{nu}{approx}1.84, {nu}{approx}1.1). addition their significance interpretation recent experiments switching ferromagnetic ferroelectric nanoparticles thin films, our provide evidence relevance universality spatially extended nonstationary systems. {copyright} 1999} American Physical Society}« less