Gate control and amplification of magnetoresistance in a three-terminal device

Gate control and amplification of magnetoresistance are demonstrated at room temperature in a fully epitaxial three-terminal GaAs-based device. In addition to the two ferromagnetic spin injector and detector electrodes of a MnAs/AlAs/GaAs:Mn/AlAs/MnAs vertical spin valve, a third non-magnetic gate electrode (Ti/Au) is placed directly on top of the heavily p-doped GaAs channel layer. The magnetoresistance of the device can be amplified to reach values as high as 500% at room temperature with the application of a bias to the gate terminal, which modulates the spin selectivity of the tunnel barriers. The experimental results are modeled by solving spin drift-diffusion and tunneling equations self consistently. (C) 2011 American Institute of Physics. [doi:10.1063/13652765]