We report the collective magnetism of the metallic altermagnet CrSb. Magnetic susceptibility and polarized neutron diffraction measurements show that CrSb is a perfectly compensated Ising altermagnet below a N\'eel temperature of TN=733(4) K. Inelastic neutron scattering experiments reveal coherent and highly-dispersive antiferromagnetic spin waves with large group velocities of 61(2) km s−1 and 58(2) km s−1 along the in-plane and out-of-plane directions, respectively. The observed magnon dispersions along high-symmetry directions of the Brillouin zone are well described by a minimal Heisenberg model up to third nearest neighbors of alternating antiferromagnetic and ferromagnetic character, J1=23(4) meV, J2=−5.4(8) meV, J3=5.2(8) meV, and an Ising single-ion anisotropy term D=0.15(4) meV. We observe clear momentum space signatures of chiral spin splitting along the low-symmetry Γ-L direction, characteristic of higher-order altermagnetic exchange interactions, the first such observation in a metallic altermagnet. These findings identify CrSb as a singular material: a metallic altermagnet in which coherent spin-split magnons persist well above room temperature, providing a compelling platform for spintronic applications.
@article{arxiv.2511.16086,
title = {Coherent high-velocity chiral magnons in the metallic altermagnet CrSb},
author = {Ashutosh K. Singh and Niclas Heinsdorf and Abraham A. Mancilla and Jörn Bannies and Avishek Maity and Alexander I. Kolesnikov and Masaaki Matsuda and Matthew B. Stone and Marcel Franz and Jonathan Gaudet and Alannah M. Hallas},
journal= {arXiv preprint arXiv:2511.16086},
year = {2026}
}