Spin-injection experiments in NiFe/two-dimensional electron gas (2DEG)/NiFe four-terminal devices are described. The 2DEG was confined at a modulation-doped In0.75Ga0.25As/In0.75Al0.25As heterojunction interface. NiFe source-drain electrodes were located ∼ 1 μm apart and two voltage probes were fabricated between them. The separation between the NiFe electrodes was thus almost less than both the mean free path (∼ 2 μm) and the spin-diffusion length (> 1 μm) of the 2DEG. In nonlocal four-terminal measurements, where a constant current (i) was sent through one NiFe to one ohmic electrode, the two-terminal magnetoresistance (R2t = V2t/i) exhibited a spin-valve-like effect, while R4t = V4t/i showed a resistance hysteresis. The amplitude of the latter amounted to almost 12% of the R4t (B = 0) at 1.5 K, the extent of which was one order of magnitude larger than those so far reported. These results suggest the importance of a quasi-ballistic as well as a spin-coherent coupling between the two NiFe electrodes, which may crucial in the future operation of spin field-effect transistors (FETs).
|ジャーナル||Japanese Journal of Applied Physics, Part 2: Letters|
|出版ステータス||Published - 2001 10月 15|
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