Increase of nonlocal spin signal at high dc bias due to a redistribution of the injection current

The spin signals in nonlocal spin valves with 1.3 nm AlOx layers as spin-injection and spin-detection interfaces have been measured as a function of the dc bias current through the injector. Increases of the spin signals have been observed in both polarities of the injection current, with magnitudes up to 81%. This is attributed to a redistribution of the injection current due to a nonlinear resistivity at a higher bias. The baseline of the spin signal varies as a function of the bias current as well, and it is consistent with the interpretation of current redistribution. A temperature dependence of the spin signals has been conducted to demonstrate that the 81% increase of spin signal cannot be accounted for by the Joule heating of the device.