# Capturing ultrafast magnetic dynamics by time-resolved soft x-ray magnetic circular dichroism

## TL;DR

This paper demonstrates the use of time-resolved soft x-ray magnetic circular dichroism with sub-50 ps resolution to observe ultrafast demagnetization in FePt thin films, highlighting the technique's potential for studying rapid magnetic dynamics.

## Contribution

It introduces a novel experimental setup combining Tr-XMCD with high time resolution and compares PEY and TFY modes for analyzing ultrafast magnetic phenomena.

## Key findings

- Ultrafast demagnetization observed within 50 ps in FePt films
- PEY mode provides less-distorted spectra suitable for sum rule analysis
- Demagnetization threshold depends on photon density

## Abstract

Experiments of time-resolved x-ray magnetic circular dichroism (Tr-XMCD) and resonant x-ray scattering at a beamline BL07LSU in SPring-8 with a time-resolution of under 50 ps are presented. A micro-channel plate is utilized for the Tr-XMCD measurements at nearly normal incidence both in the partial electron and total fluorescence yield (PEY and TFY) modes at the L2,3 absorption edges of the 3d transition-metals in the soft x-ray region. The ultrafast photo-induced demagnetization within 50 ps is observed on the dynamics of a magnetic material of FePt thin film, having a distinct threshold of the photon density. The spectrum in the PEY mode is less-distorted both at the L2,3 edges compared with that in the TFY mode and has the potential to apply the sum rule analysis for XMCD spectra in pump-probed experiments.