Enhanced subterahertz spin-current transients via modulation of cross-sublattice damping in uniaxial antiferromagnets

Abstract

We present an analytical model to compute the subterahertz (sub-THz) spin current transients injected from the insulating uniaxial antiferromagnet (AFM) into the adjacent nonmagnetic layer excited by spin pumping under the antiferromagnetic resonance condition, where both intra- and cross-sublattice damping parameters are treated on an equal footing. As expected, the sub-THz spin-pumping signal decreases with larger intra-sublattice damping dissipation. Interestingly, it is found that the amplitude of the spin current transient is enhanced with increasing cross-sublattice damping. On the other hand, the spin pumping is reduced by increasing the cross-sublattice spin-mixing conductance. These trends indicate that the intrinsic origin of the cross-sublattice damping in the bulk AFM enhances the spin current transients while its extrinsic origin, directly related to the interfacial cross-sublattice spin-mixing conductance, has the opposite effect. Our results suggest the important role of the previously neglected cross-sublattice damping in modulating the sub-THz spin current pulses for ultrafast spintronic applications.