Inverse Local Magnetoresistance Effect Up to Room Temperature in Ferromagnet-Semiconductor Lateral Spin-Valve Devices

We find relatively large inverse local two-terminal magnetoresistance (MR) effect in ferromagnet (FM)/semi-conductor (SC) lateral spin-valve devices. The local MR as a function of the bias voltage applied between two FM/SC contacts shows nonlinear variation, including sign inversion in high bias-voltage conditions. The inverse local MR can be observed up to room temperature, while conventional positive local MR disappears at around 225 K. To consider the origin of the large inverse MR effect, the influence of the nonlinear spin-detection efficiency at a biased FM/SC contact and the spin-drift effect in the SC channel are discussed.