Ultrafast demagnetization of Pt magnetic moment in L1${}_0$-FePt probed by hard x-ray free electron laser

TL;DR

This study uses hard x-ray free electron laser techniques to observe ultrafast demagnetization in L1${}_0$-FePt, revealing distinct decay times for Pt and total magnetization and demonstrating transient magnetic states.

Contribution

First demonstration of ultrafast demagnetization of Pt in L1${}_0$-FePt using hard x-ray free electron laser and time-resolved x-ray magnetic circular dichroism.

Findings

Pt demagnetization decay time: 0.6 ps

Total magnetization decay time: 0.1 ps

Transient magnetic state with modulated 3d-5d coupling

Abstract

We demonstrate ultrafast magnetization dynamics in a 5d transition metal using circularly-polarized x-ray free electron laser in the hard x-ray region. A decay time of light-induced demagnetization of L1${}_0$-FePt was determined to be $\tau_\textrm{Pt} = 0.6\ \textrm{ps}$ using time-resolved x-ray magnetic circular dichroism at the Pt L${}_3$ edge, whereas magneto-optical Kerr measurements indicated the decay time for total magnetization as $\tau_\textrm{total} = 0.1\ \textrm{ps}$. A transient magnetic state with the photo-modulated magnetic coupling between the 3d and 5d elements is firstly demonstrated.