Quantitative estimation of thermoelectric contributions in spin pumping signals through microwave photoresistance measurements

Abstract

Spin pumping is a technique widely used to generate pure spin current and characterize the spin-charge conversion efficiency of heavy metals. Upon microwave excitation, the sample may also be heated, and the parasitic thermoelectric signals could contaminate the spin pumping results. Owing to their identical angular dependences with respect to the magnetic field, it is difficult to isolate one from the other. In this paper, we present a quantitative method to separate thermoelectric contributions from spin pumping signals in both $\mathrm{Py}({\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20})/\mathrm{Pt}$ and $\mathrm{YIG}({\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12})/\mathrm{Pt}$ bilayers through microwave photoresistance measurements. We find that the microwave absorption indeed can raise the temperature of samples, resulting a field-dependent thermoelectric hysteresis loop. However, the additional heat dissipation due to the resonant precession of the magnetization in the ferromagnet is negligibly small compared with the measured spin pumping signal. Thus, we conclude that the spin pumping signal is free of any detectable thermoelectric contributions.