Ferromagnetic Thin Layers for Spin Polarimetry

We present a study of spin filtering effect in a ferromagnetic metal/semiconductor (Pd/Fe/oxide/GaAs) junction and discuss the application to electron spin polarimetry. Spin-polarized electrons are injected from vacuum in the metallic layer and the current I_C transmitted through the junction is collected in the semiconductor substrate. When reversing the magnetization of the Fe layer, a spin-dependent component of the transmitted current ΔI_C is measured. The transmission spin asymmetry ΔI_C/2I_C is proportional to the polarization P₀ of the incident electrons. Both I_C and ΔI_C increase over several orders of magnitude with the energy E_P of the incoming electrons. We show that adjusting E_P allows to optimize the measurement of P₀.