Evidence of itinerant electron-local moment interactions in altermagnetic Li-doped MnTe

MnTe hosts an altermagnetic ground state – an elementary type of collinear magnetic order where alternating magnetic moments are distinguished by their local environment. Altermagnets are expected to host a number of unconventional phenomena including non-relativistic spin splitting of electronic bands, anomalous Hall effect, and non-degenerate chiral magnons. The latter has been directly observed in MnTe via inelastic neutron scattering (INS) measurements. The addition of less than 1% Li doping to MnTe causes a dramatic spin reorientation from in-plane to out-of-plane. An open question is how Li doping affects the altermagnetic phenomenology in this system. To answer this question, we performed high-resolution inelastic neutron scattering measurements on a ~2 g single crystal of 3% Li-doped MnTe. Along the directions where splitting is expected in undoped MnTe, we find no evidence for chiral splitting in Li-doped MnTe and instead find that the spin wave linewidth is substantially broadened relative to undoped MnTe, while the overall spin wave bandwidth is slightly reduced. We also report on the local dynamic susceptibility extracted from the absolute intensity of the INS spectra, and find good agreement between the experimentally observed total effective moment and the expected magnitude for S=5/2 Mn²⁺ local moments in both parent and Li-doped MnTe. These findings suggest that the increased metallicity induced by 3% Li doping results in enhanced interactions between itinerant electrons and local moments, providing valuable insight into how charge doping affects the altermagnetic phenomenology in this system.