Speed limit of FePt spin dynamics on femtosecond timescales

TL;DR

This paper investigates the ultrafast magnetization dynamics of FePt materials, revealing a fundamental speed limit for heat-assisted magnetic recording due to a transition to slower demagnetization processes.

Contribution

It introduces a thermal micromagnetic model to simulate FePt dynamics and identifies a transition to type II behavior linked to electron temperature, setting a speed limit for recording.

Findings

Identification of a transition to type II demagnetization behavior.

Relation of slowing down to electron temperatures from laser heating.

Fundamental speed limit for heat-assisted magnetic recording.

Abstract

Magnetization manipulation is becoming an indispensable tool for both basic and applied research. Theory predicts two types of ultrafast demagnetization dynamics classified as type I and type II. In type II materials, a second slower process takes place after the initial fast drop of magnetization. In this letter we investigate this behavior for FePt recording materials with perpendicular anisotropy. The magnetization dynamics have been simulated using a thermal micromagnetic model based on the Landau-Lifshitz-Bloch equation. We identify a transition to type II behavior and relate it to the electron temperatures reached by the laser heating. This slowing down is a fundamental limit to reconding speeds in heat assisted reversal.