Spin waves in the intermetallic compound MnNi

The intermetallic compound MnNi with tetragonal structure, with the highest value, among the 3d metal alloys, of the Neel temperature and a high magnetic moment, presents a unique case for a study of 3d alloy antiferromagnets. Its highly anisotropic arrangement of spins implies a strong anisotropy of various properties. The expected anisotropy of spin-wave velocity is not confirmed. In addition, the very small value of the spin-wave-damping parameter is in strong contrast to the high damping found in all γ-Mn alloys. This difference can be explained by different electron band structures.