The dc voltage obtained from the inverse spin Hall effect (iSHE) due to spin pumping in ferromagnet/normal-metal (NM) bilayers can be unintentionally superimposed with magnetoresistive rectification of ac charge currents in the ferromagnetic layer. W
e introduce a geometry in which these spurious rectification voltages vanish while the iSHE voltage is maximized. In this geometry, a quantitative study of the dc iSHE is performed in a broad frequency range for Permalloy/NM multilayers with NM={Pt, Ta, Cu/Au, Cu/Pt}. The experimentally recorded voltages can be fully ascribed to the iSHE due to spin pumping. Furthermore we measure a small iSHE voltage in single CoFe thin films.
An intriguing feature of spintronics is the use of pure spin-currents to manipulate magnetization, e.g., spin-currents can switch magnetization in spin-torque MRAM, a next-generation DRAM alternative. Giant spin-currents via the spin Hall effect grea
tly expand the technological opportunities. Conversely, a ferromagnet/normal metal junction emits spin-currents under microwave excitation, i.e. spin-pumping. While such spin-currents are modulated at the excitation frequency, there is also a non-linear, rectified component that is commonly detected using the corresponding inverse spin Hall effect (iSHE) dc voltage. However, the ac component should be more conducive for quantitative analysis, as it is up to two orders of magnitude larger and linear. But any device that uses the ac iSHE is also sensitive to inductive signals via Faradays Law and discrimination of the ac iSHE signal must rely on phase-sensitive measurements. We use the inductive signal as a reference for a quantitative measurement of the magnitude and phase of the ac iSHE.
A Comment on Phys. Rev. Lett. 111, 217204 (2013), Detection of Microwave Spin Pumping Using the Inverse Spin Hall Effect
