ABSTRACT
This chapter deals with one phenomenon called spin filter tunneling, hotly pursued for its capability to provide tunable P all the way to near 100% and can be interfaced with metals, semiconductors or superconductors, giving the versatility for exploring new effects. The exchange splitting of the conduction band in europium chalcogenides is substantial, the largest being 0.54 eV for europium, making them ideal candidates as spin filter materials. The initial demonstration of spin filter tunneling using the Meservey-Tedrow technique was performed with a ferromagnetic EuS barrier. Stoichiometric EuO is quite difficult to grow at the few monolayers scale necessary for tunneling, due to the formation of the more stable and non-magnetic Eu2O3 which is not a spin filter. The spin filter effect in the ferromagnetic semiconductor GdN shows a different behavior to that observed for EuS and EuO. The early experiments with spin filter tunnel barriers showed the spin filter effect by using the Meservey-Tedrow technique.
