Spin pumping is one of the most common ways to generate the desired spin current in experiment. With much shorter timescales than in ferromagnets (FM), antiferromagnetic (AFM) spin dynamics can offer much more attractive properties for potential applications in ultrafast spintronics devices. In recent years, although the AFM sub-terahertz spin pumping has been sucessfully observed, there is still some debate over the existence of cross-sublattice spin pumping in AFM. Here, we start from the most general form of AFM spin pumping and phenomenologically derive its Onsager reciprocal effect--current induced torque. By symmetry analysis we argue that the off-diagonal elements of spin-mixing conductance in net magnetization m and Neel vector n basis must vanish for a collinear AFM. The anti-damping like torques and cross-sublattice torques are shown to be proportional to the symmetric and asymmetric parts of the diagonal spin-mixing conductance respectively. For a conclusive evidence, we explicitly derive a more general form of spin-mixing conductance by scattering matrix method. For a insulating compensated AFM interface, the asymmetric parts of the diagonal spin-mixing conductance vanishes, manifesting the absence of cross-sublattice torques and spin pumping in collinear AFM.

References
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