Electrical detection of spin pumping: dc voltage generated by ferromagnetic resonance at ferromagnet/nonmagnet contact

We describe electrical detection of spin pumping in metallic nanostructures. In the spin pumping effect, a precessing ferromagnet attached to a normal metal acts as a pump of spin-polarized current, giving rise to a spin accumulation. The resulting spin accumulation induces a backflow of spin current into the ferromagnet and generates a dc voltage due to the spin dependent conductivities of the ferromagnet. The magnitude of such voltage is proportional to the spin-relaxation properties of the normal metal. By using platinum as a contact material we observe, in agreement with theory, that the voltage is significantly reduced as compared to the case when aluminum was used. Furthermore, the effects of rectification between the circulating rf currents and the magnetization precession of the ferromagnet are examined. Most significantly, we show that using an improved layout device geometry, these effects can be minimized.