Spin transfer torques in AF

Spin Pumping and Spin-Transfer Torques in Antiferromagnets.
Ran Cheng, Jiang Xiao, Qian Niu, and Arne Brataas
Phys. Rev. Lett. 113, 057601 (2014)

The two eigenmodes of Eq. (2) have opposite chiralities and opposite ratios between the cone angles of m1 and m2. A magnetic field along the easy axis breaks the degeneracy of the two modes.