Gate-control of spin-motive force and spin-torque in Rashba SOC systems

Abstract

The introduction of a strong Rashba spin–orbit coupling has been predicted to enhance the spin motive force (SMF) (see Kim et al 2012 Phys. Rev. Lett. http://dx.doi.org/10.1103/PhysRevLett.108.217202 108 http://dx.doi.org/10.1103/PhysRevLett.108.217202 ). In this work, we predict further enhancement of the SMF by time modulation of the Rashba coupling ${\alpha }_{{\rm{R}}}$ , which induces an additional electric field ${E}_{d}^{R}={\dot{\alpha }}_{{\rm{R}}}{m}_{{\rm{e}}}/e{\rm{\hslash }}(\hat{z}\times m)$ . When the modulation frequency is higher than the magnetization precessing frequency, the amplitude of this field is significantly larger than previously predicted results. Correspondingly, the spin torque on the magnetization is also effectively enhanced. We also suggest a biasing scheme to achieve rectification of SMF, i.e., by application of a square wave voltage at the resonant frequency. Finally, we numerically estimate the resulting spin torque field arising from a Gaussian pulse time modulation of ${\alpha }_{{\rm{R}}}$ .

Keywords

• magnetization dynamics
• spin–orbit coupling
• spin-motive force
• 75.78.-n
• 71.70.Ej
• 85.75.-d