Oscillatory changes in the tunneling magnetoresistance effect in semiconductor quantum-dot spin valves
K. Hamaya, M. Kitabatake, K. Shibata, M. Jung, M. Kawamura, S. Ishida, T. Taniyama, K. Hirakawa, Y. Arakawa, and T. Machida

We experimentally study tunneling magnetoresistance (TMR) effect as a function of bias voltage ($V$$_\mathrm{SD}$) in lateral Ni/InAs/Ni quantum-dot (QD) spin valves showing the Coulomb blockade characteristics. With varying $V$$_\mathrm{SD}$, the TMR value oscillates, and the oscillation period corresponds to conductance changes observed in current-voltage ($I -$$V$$_\mathrm{SD}$) characteristics. We also find 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.

© 2008 The American Physical Society.