Finite size effects on the ultrafast remagnetization dynamics of FePt

TL;DR

This study examines how finite size influences the ultrafast remagnetization process in FePt films, revealing that film structure and magnetic field strength significantly affect the speed and mechanisms of magnetization recovery.

Contribution

It provides new insights into the role of finite size and film structure on ultrafast magnetization dynamics in FePt, especially under different magnetic fields.

Findings

Remagnetization speeds increase with magnetic field in continuous films.

Domain wall motion governs dynamics in continuous films.

Heat transport dominates in high fields for continuous films, cooling times dominate in granular films.

Abstract

We investigate the ultrafast magnetization dynamics of FePt in the L10 phase after an optical heating pulse, as used in heat assisted magnetic recording. We compare continuous and nanogranular thin films and emphasize the impact of the finite size on the remagnetization dynamics. The remagnetization speeds up significantly with increasing external magnetic field only for the continuous film, where domain wall motion governs the dynamics. The ultrafast remagnetization dynamics in the continuous film are only dominated by heat transport in the regime of high magnetic fields, whereas the timescale required for cooling is prevalent in the granular film for all magnetic field strengths. These findings highlight the necessary conditions for studying the intrinsic heat transport properties in magnetic materials.