Nonlocal, local, and extraction spin valves based on ferromagnet/semiconductor hybrid structures consisting of the Heusler alloy Co2FeSi on GaAs

Abstract

We demonstrate electrical injection, extraction and detection of spin polarization in a lateral transport structure consisting of ferromagnetic Co 2 FeSi stripes on a nonmagnetic n -GaAs transport channel. For the lateral transport based on electrical spin injection, the characteristic spin-valve signatures are observed both in the nonlocal and local configurations. The comparatively large magnitude of the local spin valve signal and the high signal-to-noise ratio are attributed to the large spin polarization at the Fermi energy of Co 2 FeSi in the well-ordered L 2 1 phase. Furthermore, we elucidate a device concept in which the basic building block consists of a local spin valve utilizing spin extraction instead of injection at the ferromagnetic stripes for its fundamental operation principle. An extended device comprises an array of such extraction-spin valves in which the spin polarization in the transport channel results from a cascade of spin extraction events. Such a multiple-extraction spin valve acts as a nonvolatile reconfigurable current divider in which a single electrical output corresponds to a particular magnetization configuration of the entire stripe array (2 m -1 electrical output levels for m ferromagnetic contacts). We discuss potential implementations of this concept for spintronic memory circuits and for sources of highly spin-polarized drift currents.