Neutron scattering study on Lithiated MnTe, an altermagnet candidate

Altermagnetism (AM) is a novel type of magnetism. In real space, the magnetic moments are compensated, but opposite-spin sublattices are connected by crystal-rotation symmetries and not by translation or inversion, making it distinct from antiferromagnetism. In reciprocal space, its electronic structures with broken time-reversal symmetry and alternating momentum-dependent sign of the spin splitting are fundamentally different from those of ferromagnetism. Magnetic excitation spectra in altermagnets depends on its chirality for wave vector q. Therefore, polarized neutrons with opposite chiralities will be scattered differently, serving as a method to distinguish altermagnets from usual antiferromagnets. Neutron scattering experiment has observed splitting in the magnetic excitation spectra, providing a crucial piece of evidence of altermagnetism. A small amount of Li doping (<5%) can change the magnetic structure: the magnetic moments rotate to the c-axis, and the in-plane component becomes negligible, thereby the crystal is detwinned. Therefore, Li-doped MnTe can serve as an ideal platform to explore AM using neutron scattering techniques.