Monte Carlo simulation of aging phenomena in multilayer magnetic structures

Alexandr N Purtov,Vladimir V Prudnikov,Pavel V Prudnikov,Marina V Mamonova,N Perov,A Semisalova

doi:10.1051/epjconf/201818503008

Abstract

A Monte Carlo simulation of the non-equilibrium behavior of multilayer magnetic structures consisting of alternating magnetic and nonmagnetic nanolayers is realized. The calculated two-time autocorrelation function for the structure during its evolution starting from high-temperature initial state is analyzed. The analysis reveals aging effects characterized by a slowing down of correlation characteristics in the system with increase of the waiting time. The dependence of aging characteristics on thickness of ferromagnetic films is investigated. It is shown that, in contrast to bulk magnetic systems, the aging effects in magnetic superstructures arise not only at the ferromagnetic ordering temperature Tc in the films but also within a wide temperature range at T ≤ Tc.

Highlights

The behavior of systems with extremely slow dynamics stays one of the intriguing problems in theoretical physics [1]. It demonstrates a wide range of interesting phenomena such as aging, and violation of the fluctuation-dissipation theorem. These features were founded in complex spin glass systems [2] but different studies of these phenomena showed that the main properties of slow dynamics can be observed in simpler systems with second-order phase transition near critical point, because the evolution of such systems is characterized by large relaxation times [3]
The nanoscale periodicity in magnetic multilayer structures gives rise to the mesoscopic effects of the spatial spin correlation with the slow relaxation dynamics of magnetization accompanying the quenching of the system in the non-equilibrium state
In contrast to the bulk magnetic systems, where the slow dynamics and aging effects manifest themselves near the critical point [4], magnetic superstructures with nanoscale periodicity allow increasing the relaxation time owing to the effects related to the larger characteristic spin-spin correlation length

Summary

Introduction

The behavior of systems with extremely slow dynamics stays one of the intriguing problems in theoretical physics [1]. Calculations of the two-time correlation functions and the staggered magnetization allow us to reveal the aging effects in the multilayer magnetic structure occurring in their non-equilibrium critical behavior at Tc and within a wide range of temperatures at T

Results

Conclusion