Current-driven ferromagnetic resonance, mechanical torques, and rotary motion in magnetic nanostructures

We study theoretically the detection and possible utilization of electric current-induced mechanical torques in ferromagnetic-normal-metal heterostructures generated by spin-flip scattering or the absorption of transverse spin currents by a ferromagnet. To this end, we analyze the dc voltage signals over a spin valve driven by an ac current. In agreement with recent studies, this "rectification," measured as a function of ac frequency and applied magnetic field, contains important information on the magnetostatics and magnetodynamics. Subsequently, we show that the vibrations excited by spin-transfer to the lattice can be detected as a splitting of the dc voltage resonance. Finally, we propose a concept for a spin-transfer-driven electric nanomotor based on integrating metallic nanowires with carbon nanotubes, in which the current-induced torques generate a rotary motion.