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岡本 尚也*; 紅林 秀和*; Trypiniotis, T.*; Farrer, I.*; Ritchie, D. A.*; 齊藤 英治; Sinova, J.*; Ma
ek, J.*; Jungwirth, T.*; Barnes, C.*
Nature Materials, 13(10), p.932 - 937, 2014/10
被引用回数：49 パーセンタイル：85.48(Chemistry, Physical)Controlling spin-related material properties by electronic means is a key step towards future spintronic technologies. The spin Hall effect has become increasingly important for generating, detecting and using spin currents, but its strength-quantified in terms of the SHE angle-is ultimately fixed by the magnitude of the spin-orbit coupling present for any given material system. However, if the electrons generating the SHE can be controlled by populating different areas of the electronic structure with different SOC characteristic the SHE angle can be tuned directly within a single sample. Here we report the manipulation of the SHE in bulk GaAs at room temperature by means of an electrical intervalley transition induced in the conduction band. The spin Hall angle was determined by measuring an electromotive force driven by photoexcited spin-polarized electrons drifting through GaAs Hall bars. By controlling electron populations in different valleys, we manipulated the angle from 0.0005 to 0.02. This change by a factor of 40 is unprecedented in GaAs and the highest value achieved is comparable to that of the heavy metal Pt.
安藤 和也*; 高橋 三郎; 家田 淳一; 紅林 秀和*; Trypiniotis, T.*; Barnes, C. H. W.*; 前川 禎通; 齊藤 英治
Nature Materials, 10(9), p.655 - 659, 2011/09
被引用回数：251 パーセンタイル：98.66(Chemistry, Physical)Injection of spin currents into solids is crucial for exploring spin physics and spintronics. There has been significant progress in recent years in spin injection into high-resistivity materials, for example, semiconductors and organic materials, which uses tunnel barriers to circumvent the impedance mismatch; the impedance mismatch between ferromagnetic metals and high-resistivity materials drastically limits the spin-injection efficiency. However, because of this problem, there is no route for spin injection into these materials through low-resistivity interfaces, that is, Ohmic contacts, even though this promises an easy and versatile pathway for spin injection without the need for growing high-quality tunnel barriers. Here we show experimental evidence that spin pumping enables spin injection free from this condition; room-temperature spin injection into GaAs from Ni
Fe
through an Ohmic contact is demonstrated through dynamical spin exchange. Furthermore, we demonstrate that this exchange can be controlled electrically by applying a bias voltage across a NiFe/GaAs interface, enabling electric tuning of the spin-pumping efficiency.
