  Magnetic resonances driven by current-induced torques are crucial tools to
study magnetic materials but are very limited in frequency and mechanical
efficiency. We propose an alternative mechanism, voltage-induced torque, to
realize high efficiency in generating high-frequency magnetization dynamics.
When a ferromagnet-topological insulator-ferromagnet trilayer heterostructure
is operated as an adiabatic quantum motor, voltage-induced torque arises from
the adiabatic motion of gapped topological electrons on the two interfaces and
act oppositely on the two ferromagnetic layers, which can excite the exchange
mode where the two ferromagnetic layers precess with a $\pi$-phase difference.
The exchange mode resonance, bearing a much higher frequency than the
ferromagnetic resonance, is accompanied by topological charge pumping, leading
to a sharp peak in electrical admittance at the resonance point. Because the
output current is purely adiabatic while dissipative current vanishes
identically, the proposed voltage-driven exchange resonance entails a
remarkably high mechanical efficiency close to unity, which is impossible in
any current-driven systems.
