Determination of the N\'eel vector in rutile altermagnets through x-ray magnetic circular dichroism: the case of MnF$_2$

TL;DR

This paper demonstrates how X-ray magnetic circular dichroism (XMCD) can be used to determine the Néel vector orientation in rutile altermagnets like MnF₂ through numerical simulations and theoretical analysis.

Contribution

It introduces a method to identify the Néel vector in rutile altermagnets using XMCD spectra and derives an exact relationship between spectra for different orientations.

Findings

XMCD spectra vary with Néel vector orientation

An exact relationship between spectra orientations is established

Numerical simulations validate the theoretical relationship

Abstract

We present a numerical simulation of the X-ray magnetic circular dichroism (XMCD) at the $L_{2,3}$ edge of Mn in altermagnetic MnF$_2$ using a combination of density functional + exact diagonlization of an atomic model. We explore how the dichroic spectra vary with the light propagation vector and the N\'eel vector. We show how XMCD in rutile structures can be employed to determine the orientation of the N\'eel vector. An exact relationship between the XMCD spectra for different orientation of the N\'eel vector valid in the absence on the valence spin-orbit coupling and core-valence multipole interaction is derived and its approximate validity demonstrated by numerical calculation for the full Hamiltonian.