Electrically tunable spin injector free from the impedance mismatch problem

電気的に制御可能なインピーダンスミスマッチフリースピン流注入源

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

Ando, Kazuya*; Takahashi, Saburo; Ieda, Junichi; Kurebayashi, Hidekazu*; Trypiniotis, T.*; Barnes, C. H. W.*; Maekawa, Sadamichi; Saito, Eiji

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 NiFe 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.