Apparatus for spin-polarized inverse photoemission and spin scattering

Spin-polarized electron sources have important applications in electron spectroscopies. Such electron spectroscopies can provide considerable insight into the electronic structure of magnetic materials. A spin-polarized electron gun, based on photoemission from a GaAs cathode, has been designed for spin- polarized inverse photoemission and spin-polarized electron scattering. Our spin-polarized electron source is used in combination with a Geiger-Muller isochromat photon detector (for inverse photoemission), a small electron energy analyzer or Mott detector (for electron spin scattering), and a pulsed magnetic field (to saturate the magnetization of the sample). It is important that such sources have very stable emission, well defined electron polarization, and excellent focus for spectroscopy applications. Much of this depends on a stable laser and associated optical systems in the near infra-red. In the instrument we describe, the geometry of the incident circularly polarized light with respect to the direction of electron emission, as well as the electron optics, are designed so that the electron spin polarization is consistently in the plane of the sample for any incident angle in an angle resolved measurements for electron wave vector dependent studies. We provide examples of the types of the novel new measurements that are possible with such instrumentation.