Magnetic exchange interactions in yttrium iron garnet: A fully relativistic first-principles investigation

Magnetic isotropic and Dzyaloshinskii-Moriya interactions in yttrium iron garnet have been obtained by ab initio fully relativistic calculations. The calculated coupling constants are in agreement with available experimental data. Using linear spin-wave theory, we are able to reproduce the experimental magnon spectrum including the spin-wave gap and stiffness. The way to calculate the exchange coupling constants using the Korringa-Kohn-Rostoker formalism for large magnetic systems such as complex oxides is discussed in detail.