Information Processing With Pure Spin Currents in Silicon: Spin Injection, Extraction, Manipulation, and Detection

We demonstrate that information can be transmitted and processed with pure spin currents in silicon. Fe/Al₂O₃ tunnel barrier contacts are used to produce significant electron spin polarization in the silicon, generating a spin current which flows outside of the charge current path. The spin orientation of this pure spin current is controlled in one of three ways: 1) by switching the magnetization of the Fe contact; 2) by changing the polarity of the bias on the Fe/Al₂O₃ "injector" contact, which enables the generation of either majority or minority spin populations in the Si, providing a way to electrically manipulate the injected spin orientation without changing the magnetization of the contact itself; and 3) by inducing spin precession through the application of a small perpendicular magnetic field. Spin polarization by electrical extraction is as effective as that achieved by the more common electrical spin injection. The output characteristics of a planar silicon three-terminal device are very similar to those of nonvolatile giant magnetoresistance metal spin-valve structures.