  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 to 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 absence of any spin relaxation processes.
