Spin-Dependent Transmission of Electrons through the Ferromagnetic Metal Base of a Hot-Electron Transistorlike System

A quasimonoenergetic spin-polarized electron beam, emitted in vacuum from a GaAs photocathode, is injected into a thin ferromagnetic metal layer deposited on an $n$-doped GaAs substrate. The current transmitted through this Schottky barrier is measured. The striking feature of this hot-electron transistorlike system is a current gain spin dependency as high as $20\%$. The measured variations of the current gain and its spin dependency with the injection energy are well explained by a very simple analytical model describing the transport of hot electrons in metallic thin films.