Element specificity of transient extreme ultra-violet magnetic dichroism

TL;DR

This study combines theory and experiment to analyze transient magnetic circular dichroism in the XUV range for bulk Co and CoPt, demonstrating element-specific magnetic dynamics and validating the approach with experimental data.

Contribution

It introduces a novel ab-initio method to simulate and interpret element-specific transient magnetic dichroism in the XUV range, bridging theory and experiment.

Findings

Element-specific local spin dynamics can be extracted from tr-MCD.

Theoretical predictions agree well with experimental measurements across multiple edges.

The method enables detailed understanding of ultrafast magnetic processes in complex materials.

Abstract

In this work we combine theory and experiment to study transient magnetic circular dichroism (tr-MCD) in the extreme ultraviolet spectral range (XUV) in bulk Co and CoPt. We use the \emph{ab-initio} method of real-time time-dependent density functional theory (RT-TDDFT) to simulate the magnetization dynamics in the presence of ultrafast laser pulses. From this we demonstrate how tr-MCD may be calculated using an approximation to the excited-state linear-response. We apply this approximation to Co and CoPt and show computationally that element-specific dynamics of the local spin moments can be extracted from the tr-MCD in XUV energy range, as is commonly assumed. We then compare our theoretical prediction for the tr-MCD for CoPt with experimental measurement and find excellent agreement at many different frequencies including the $M_{2 3}$-edge of Co and $N_{6 7}$- and $O_{2 3}$- edges of Pt.