Oscillatory changes in the tunneling magnetoresistance effect in semiconductor quantum-dot spin valves

Abstract

We experimentally study the tunneling magnetoresistance (TMR) effect as a function of bias voltage $({V}_{\mathrm{SD}})$ in lateral $\mathrm{Ni}∕\mathrm{In}\mathrm{As}∕\mathrm{Ni}$ quantum-dot (QD) spin valves showing Coulomb blockade characteristics. With varying ${V}_{\mathrm{SD}}$, the TMR value oscillates and the oscillation period corresponds to conductance changes observed in the current-voltage $(I\text{\ensuremath{-}}{V}_{\mathrm{SD}})$ characteristics. We also find an inverse TMR effect near ${V}_{\mathrm{SD}}$ values where negative differential conductance is observed. A possible mechanism of the TMR oscillation is discussed in terms of spin accumulation on the QD and spin-dependent transport properties via excited states.