Kinetic Monte Carlo Simulations of a Model for Heat-assisted Magnetization Reversal in Ultrathin Films

TL;DR

This paper uses kinetic Monte Carlo simulations to analyze heat-assisted magnetization reversal in ultrathin films, revealing optimal conditions for switching speed and providing insights for high-density magnetic recording media.

Contribution

It introduces a simulation model for HAMR in ultrathin films and explains the optimal field strength for fastest magnetization switching.

Findings

Speed-up is optimal at intermediate field strength.

Switching time depends on localized heating above critical temperature.

Results are relevant for ultrathin Co/Pt or Co/Pd multilayer media.

Abstract

To develop practically useful systems for ultra-high-density information recording with densities above terabits/cm$^2$, it is necessary to simultaneously achieve high thermal stability at room temperature and high recording rates. One method that has been proposed to reach this goal is heat-assisted magnetization reversal (HAMR). In this method, one applies a high-coercivity material, whose coercivity is temporarily lowered during the writing process through localized heating. Here we present kinetic Monte Carlo simulations of a model of HAMR for ultrathin films, in which the temperature in the central part of the film is momentarily increased above the critical temperature, for example by a laser pulse. We observe that the speed-up achieved by this method, relative to the switching time at a constant, subcritical temperature, is optimal for an intermediate strength of the writing field. This effect is explained using the theory of nucleation-induced magnetization switching in finite systems. Our results should be particularly relevant to recording media with strong perpendicular anisotropy, such as ultrathin Co/Pt or Co/Pd multilayers.