Spin-polarized photoelectron sources and spin-dependent free-electron injection through ultrathin ferromagnetic layers

The development of efficient spin-polarized electron sources, the improvement of electron spin polarimeters, and the progress in the fabrication of magnetic nanostructures and hybrid ferromagnet/semiconductor structures open up a wide field of investigation involving spin-dependent electron interactions in magnetic systems. This paper reviews the state of the art concerning spin-polarized electron sources based on semiconductor photocathodes. Their use is illustrated by the example of a new spin-dependent transmission experiment where a low-energy free-electron beam crosses a free-standing ferromagnetic thin film. It is shown that the transmission spin asymmetry reaches high values at very low primary electron energy. Possible applications of these spin-filter structures as compact and performant spin detectors are discussed, as well as perspectives for spin sensitive probes.