Alternating current-induced interfacial spin-transfer torque

We investigate an interfacial spin-transfer torque and beta-term torque with alternating current (AC) parallel to a magnetic interface. We find that both torques are resonantly enhanced as the AC frequency approaches the exchange splitting energy. We show that this resonance allows us to estimate directly the interfacial exchange interaction strength from the domain wall motion. We also find that the beta term includes an unconventional contribution which is proportional to the time derivative of the current and exists even in the absence of any spin relaxation processes.