Magnon dispersion relations in the noncollinear antiferromagnet IrMn3

The noncollinear L12−IrMn3 room-temperature metallic antiferromagnet is one of the most important materials for scientific investigation and for applications in antiferromagnetic spintronics. It has been subject to intense investigation for over two decades, mainly in connection with exchange bias phenomena. Here we present a theoretical calculation of the magnon dispersion relations and the experimental observation of some magnon modes using inelastic Brillouin and Raman light-scattering techniques. The fit of theory to the experimentally measured magnon frequencies yields values for the nearest-neighbor AF exchange, the next-nearest-neighbor FM exchange interaction, and the uniaxial anisotropy parameters that are in good agreement with the ones calculated with atomistic spin models. The knowledge of the magnon dispersion relations revealed here is essential for the study of possible applications of IrMn3 in terahertz and other spintronic devices.