Inverse spin Hall effect observed in silicon
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Inverse spin Hall effect observed in silicon
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esigners of next-generation electronics are trying to take advantage of both the electron’s charge and spin. The success of spintronic devices therefore hinges on the ability to convert between spin and charge currents. The direct spin Hall effect is typically used to probe spin-orbit coupling in these materials, but the technique cannot be applied to semiconductors with long spin lifetimes, such as indirect bandgap silicon. Researchers Kazuya Ando and Eiji Saitoh at Tohoku University in Sendai, Japan, have turned their attention to the inverse spin Hall effect (ISHE), which makes use of the high resistivity of semiconductors to detect tiny spin currents. Ando and Saitoh show that it is possible to study spin-orbit interactions using ISHE in otherwise unmeasurable systems. As reported in the January 17 issue of the online journal Nature Communications (DOI: 10.1038/ncomms1640), the researchers first deposited a thin-film heterostructure of Ni81Fe19/B-doped Si onto a silicon-on-insulator substrate and laid down ohmic AuPd contacts to detect the in-plane Hall voltage. They then measured the voltage across
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VOLUME 37 • MARCH 2012
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independent devices also allowed the team to make simultaneous measurements on the same cell or at multiple sites on a cell monolayer. With the poten-
tial for attaining dimensions as small as 5 nm, these devices could become a useful new tool in electrophysiology. Tobias Lockwood
the AuPd contacts with a maga netic field applied at 0° and 180° normal to the plane of the sample. They found that the Hall voltage depends on the direction of the magnetic field around the ferromagnetic resonance edge, which is indicative of the ISHE effect. The researchers next measb ured the voltage dependence on the angle of the out-of-plane magnetic field. This revealed that a spin current is injected into the Si layer and that it precesses around an axis parallel to the applied magnetic field (see figure). Using the Landau– Lifshitz–Gilbert equation, Ando and Saitoh were able to demon(a) Schematic of the Ni81Fe19/Si sample in strate dynamical spin injection in spintronics study; (b) the precession of spins in the silicon layer measured by the inverse spin p-type silicon at room temperaHall effect (ISHE). H is applied oblique to the film ture and unambiguously extract plane; M denotes the static component of the the ISHE contribution from the magnetization; θ and φ show the magnetic field angle and magnetization angle, respectively; and silicon layer. This technique can js is the spin current. Reproduced with permisbe used to explore the spin Hall sion from Nat. Commun., DOI: 10.1038/ ncomms1640. © 2012 Macmillan Publishers Ltd. effect in silicon wi
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