Hysteresis and training effect in the electric control of spin current in Pt/Y3Fe5O12 heterostructures

Abstract

We have reported on the hysteresis and training effect of spin current in $\mathrm{Pt}/{\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ heterostructures during subsequent cycles of ionic liquid gate voltage ${V}_{g}$. The inverse spin Hall effect voltage in spin pumping and spin Hall magnetoresistance exhibit diode-like behaviors in the first half cycle of ${V}_{g}$ and also show hysteresis in the first cycle of ${V}_{g}$. Both the diode-like behavior and the hysteresis become weak and even vanish in the second cycle of ${V}_{g}$ due to the training effect. The above experimental results can be well explained by the screening charge doping model, in which the charge and the local magnetic moment are asymmetrically distributed in the Pt layer. The applicability of this model is further confirmed by measurements of anisotropic magnetoresistance and ferromagnetic resonance. The diode-like behavior is attributed to interplay between the asymmetrically distributed local magnetic moment and the spin current relaxation in the Pt layer. The hysteresis and the training effect arise from the incompletely reversible process between oxidation and reduction of Pt atoms and the evolution of the surface morphology at the ionic liquid/Pt interface under electric gating. This work provides new insights to improve the functional performance of electrically controlled spin current devices.