Altermagnets, a unique class of magnetic materials that combines features of both ferromagnets and antiferromagnets, have garnered attention for their potential in spintronics and magnonics. While the electronic properties of altermagnets have been well studied, characterizing their magnon excitations is essential for fully understanding their behavior and enabling practical device applications. In this work, we introduce a measurement protocol combining resonant inelastic X-ray scattering with circular polarization and azimuthal scanning to probe the chiral nature of the altermagnetic split magnon modes in CrSb. This approach circumvents the challenges posed by domain averaging in macroscopic samples, allowing for precise measurements of the polarization and energy of the magnons in individual antiferromagnetic domains. Our findings demonstrate a pronounced circular dichroism in the magnon peaks, with an azimuthal dependence that is consistent with the theoretical predictions and the g-wave symmetry. By establishing a reliable and accessible method for probing altermagnetic magnons, this work opens new avenues for fundamental studies of these collective excitations and for developing next-generation magnonic device applications.

Department of Condensed Matter Physics Faculty of Mathematics and Physics Charles University Praha Czechia

Diamond Light Source Harwell Campus Didcot OX11 0DE UK

National Synchrotron Radiation Laboratory and School of Nuclear Science and Technology University of Science and Technology of China Hefei China

Scientific Computing Department STFC Daresbury Laboratory Warrington UK

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Systematic mapping of altermagnetic magnons by resonant inelastic X-ray circular dichroism