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(Color online) (a) Schematic diagram of the device geometry and three-terminal Hanle measurement. (b) Typical J-V characteristics of the CoFe(5 nm)/MgO(2 nm)/n-Ge tunnel contact with a heavily doped surface layer (sample C) at 300 K, together with the reference contact without the heavily doped layer (sample R) for comparison. (c) Associated RA products at a bias voltage of −0.25 V for different temperatures.
(Color online) (a) ΔV across the sample C and (b) the sample R as a function of the B ⊥ at 300 K for I of 500 and 50 (, spin injection/extraction condition), respectively. The solid line represents the Lorentzian fit. The closed circle shows the in-plane measurement (). (c) ΔV vs. B ⊥ over the full T range of 5-300 K for the sample C. (d) ΔV and effective vs. Tat the I of 500 (solid symbol()/open symbol()) for the sample C.
(Color online) (a) ΔV and (b) effective vs. up to mA over the entire T range of 5–300 K. The corresponding Vb for I = −3 mA (+3 mA) is −0.98 V (+0.65 V) at 5 K and −0.54 V (+0.31 V) at 300 K, respectively. (c) Hanle curves obtained at 5 K for the both bias polarities. The dashed line represents background signal. (d) Expanded vs. Vb (=VFM – VGe ) up to 0.5 V for the T range of 5–100 K (note that we took the − plot instead of the −I plot to analyze the region showing inverted Hanle effect under energy dimension). The corresponding I for Vb = −0.5 V (+0.5 V) is −0.20 mA (+0.70 mA) at 5 K and −0.45 mA (+1.60 mA) at 100 K, respectively. The dashed line represents the sign reversal region ( < 0 under Vb > 0). It is noted that the inverted Hanle signal shows a peak around Vb = +0.2 V (or I = (5 K)).
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