Detection of ferroic octupole ordering in -wave altermagnetic rutile-type compounds
Phys. Rev. B 113, 235105 – Published 1 June, 2026
DOI: https://doi.org/10.1103/d9r5-8hy8
Abstract
We propose that x-ray absorption and emission magnetic circular dichroism (XAS-MCD and XES-MCD) are promising measurements to directly detect ferroic higher-rank multipoles as candidate order parameters in altermagnets. Using the sum rules for XES-MCD and connecting them to multipole language, we demonstrate that the expectation value of the magnetic octupole moment is finite in the -wave altermagnetic candidate rutile-type compounds (T = transition metal). We also perform spectral calculations of XAS-MCD and XES-MCD based on an effective model with a full multiplet approach. While the intensity of the XAS-MCD spectra vanishes, the XES-MCD spectra exhibit finite intensity, whose spectrum becomes opposite by inverting the Néel vector. These results clearly indicate ferroic magnetic octupole order in these compounds.
