SPIN-FILTER EFFECT OF THE EUROPIUM CHALCOGENIDES - AN EXACTLY SOLVED MANY-BODY MODEL

A model Hamiltonian is introduced which considers the main features of the experimental spin-filter situation such as s-f interaction, plana r geometry, and the strong external electric field. The proposed many- body model can be solved analytically and exactly using Green function s. The spin polarization of the field-emitted electrons is expressed i n terms of spin-flip probabilities, which are put down to the exactly known dynamic quantities of the system. The calculated electron spin p olarization shows remarkable dependencies on the electron velocity per pendicular to the emitting plane and the strength of s-f coupling. Exp erimentally observed polarization values of about 90% are well underst ood within the framework of the proposed model.