Spin-Guide: A New Source of High Spin-Polarized Current

We propose a ``spin-guide'' source for generation of electric currents with a high degree of spin polarization, allowing long-distance transmission of the spin-polarization. In the spin-guide scheme proposed here, a non-magnetic conducting channel is wrapped by a magnetic shell which preferentially transmits electrons with a particular spin polarization. It is shown that this method is significantly more effective then the spin-filter-like scheme where the current flows perpendicular to the interface between a ferromagnetic metal to a non-magnetic conducting material. Under certain conditions a spin-guide may generate an almost perfectly spin-polarized current, even when the magnetic material used is not fully polarized. The spin-guide is predicted to allow the transport of spin polarization over long distances which may exceed significantly the spin-flip length in the channel. In addition, it readily permits detection and control of the spin-polarization of the current. The spin-guide may be employed for spin-flow manipulations in semiconductors used in spintronic devices.