Vector spectroscopy for spin pumping

Abstract

We propose a method to separate the inverse spin Hall effect (ISHE) from galvanomagnetic effects in spin pumping experiments on metallic bilayer systems by measuring the dc electromotive force in two orthogonal directions. Calculations of dc voltages in longitudinal and Hall directions induced in ${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}$ and ${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}\text{/}\mathrm{Pt}$ films at ferromagnetic resonance in a microwave cavity predict that contributions from ISHE and from the galvanomagnetic effects, i.e., the anisotropic magnetoresistance and the anomalous Hall effect, exhibit distinct signal symmetry as well as angular dependence when changing the direction of the external field with respect to the film plane. According to measurements on ${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}\text{/}\mathrm{Pt}$, only that dc voltage component which includes ISHE is more than five times larger than purely galvanomagnetic components. This is corroborated by results on ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_{3}\text{/}\mathrm{Pt}$ samples, demonstrating universality of this method.