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Non-local voltage normalized to the current magnitude vs. magnetic field for positive (red solid) and negative (dotted blue) currents, measured for a Ag/Py device with d = 500 nm at T = 4.2 K. (a) I = 1.5 mA, NLSV signals are the same. (b) I = 4 mA, NLSV signal for positive current (red solid bar) is larger than that for negative current (blue dotted bar). Inset in (a) shows scanning electron microscope image of the device. Py electrodes (blue) and NM bar (colored orange) are shown. Notice areas of overlap and small area where only Py exists. Current direction and voltage setup are marked.
(a) NLSV signal vs. current measured for a Py/Cu device with d = 230 nm at T = 4.2 K. Measurements are done with positive currents (red empty circles), negative currents (blue full circles), and dc-reversal (black triangles). Green empty triangles are the averages of positive and negative current measurements. (b) NLSV signal vs. temperature of the same device measured at I = 0.2 mA, for positive currents, negative currents, and dc-reversal. (c) NLSV signal vs. FM electrode spacing d (same sample), measured for I = ±5 mA. The y-axis is logarithmic scale.
(a) and (b) Py/Cu device. Cu spin diffusion length (a) and Py spin polarization (b) vs. current amplitude for positive currents (red empty circles), negative currents (blue full circles), and dc-reversal (black triangles). (c) and (d) Same for Py/Ag device. Inset: Difference between spin polarization of positive and negative currents vs. current magnitude. Red full squares correspond to Py/Cu system, and blue empty squares to Py/Ag. Straight lines are guides to the eye.
Cartoon model of both the current-induced spin injection (black spins) and thermally induced spin injection (red spins). For positive current (a), the up-spins combine to provide a larger signal, while negative currents (b) result in a smaller spin accumulation. The detecting electrode signal is proportional to the injection.
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