title: Electrically tunable spin injector free from the impedance mismatch problem.
abstract: 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 problem; 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(81)Fe(19) 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 Ni(81)Fe(19)/GaAs interface, enabling electric tuning of the spin-pumping efficiency.
authors.forename: K
authors.initials: K
authors.lastname: Ando
authors.forename: S
authors.initials: S
authors.lastname: Takahashi
authors.forename: J
authors.initials: J
authors.lastname: Ieda
authors.forename: H
authors.initials: H
authors.lastname: Kurebayashi
authors.forename: T
authors.initials: T
authors.lastname: Trypiniotis
authors.forename: C H W
authors.initials: CH
authors.lastname: Barnes
authors.forename: S
authors.initials: S
authors.lastname: Maekawa
authors.forename: E
authors.initials: E
authors.lastname: Saitoh