Critical disorder and critical magnetic field of the nonequilibrium athermal random-field Ising model in thin systems

Abstract

© 2019 American Physical Society. In the present study of the nonequilibrium athermal random-field Ising model we focus on the behavior of the critical disorder Rc(l) and the critical magnetic field Hc(l) under different boundary conditions when the system thickness l varies. We propose expressions for Rc(l) and Hc(l) as well as for the effective critical disorder Rceff(l,L) and effective critical magnetic field Hceff(l,L) playing the role of the effective critical parameters for the L×L×l lattices of finite lateral size L. We support these expressions by the scaling collapses of the magnetization and susceptibility curves obtained in extensive simulations. The collapses are achieved with the two-dimensional (2D) exponents for l below some characteristic value, providing thus a numerical evidence that the thin systems exhibit a 2D-like criticality which should be relevant for the experimental analyses of thin ferromagnetic samples.