Aging Effects in the Nonequilibrium Behavior of Magnetic Superstructures and Their Manifestation in Magnetoresistance

Abstract

The nonequilibrium behavior of the magnetic superstructures consisting of alternating magnetic and nonmagnetic nanolayers is numerically simulated by Monte Carlo methods. An analysis of the calculated two-time dependence of an autocorrelation function during the evolution from a high-temperature initial state has revealed aging effects, which are characterized by slowing down of the correlation effects in the system when the waiting time increases. In contrast to bulk magnetic systems, the aging effects are shown to appear in magnetic superstructures both near the critical ferromagnetic ordering temperature T_c in films and in a low-temperature phase at T ≤ T_c. The aging effects in the correlation processes in a magnetic multilayer structure weaken when ferromagnetic film thickness N increases at T = T_c(N), and these effects increase with film thickness N at temperatures T = T_c(N)/2. When simulating the transport properties of the Co/Cu(001)/Co structure, we calculated the temperature dependence of equilibrium magnetoresistance and were the first to reveal the influence of nonequilibrium behavior of the structure on the magnetoresistance and the manifestation of the aging effects in it.