Theory of spin-transfer torques in antiferromagnetic textures

反強磁性テクスチャにおけるスピントランスファートルクの理論

家田 淳一   ; 山根 結太*; Sinova, J.*

Ieda, Junichi; Yamane, Yuta*; Sinova, J.*

We present a theory of spin-transfer torques in textured antiferromagnets considering the small and large limits of the exchange coupling energy relative to the kinetic energy of the inter-sublattice electron dynamics. Our theory suggests a natural definition of the efficiency of spin-transfer torques in antiferromagnets in terms of well-defined material parameters, revealing that the charge current couples predominantly to the antiferromagnetic order parameter and the sublattice-canting moment in, respectively, the limits of large and small exchange coupling. The effect leads to antiferromagnetic domain wall motion and the characteristic Doppler shift in the antiferromagnetic spin-wave dispersions. The same formalism also predicts a cross effect of magnetic field gradient and charge current on a antiferromagnetic domain wall motion. The findings offer a framework for understanding and designing spin-transfer torques in antiferromagnets belonging to different classes of sublattice structures.