Magnetoresistance of magnetic tunnel junctions in the presence of a nonmagnetic layer

A quantum-statistical theory of electron tunneling in magnetic junctions of the form F/P/O/F, where F and P are, respectively, a magnetic and a parama gnetic metal is presented. The effect of scattering at the P/O interface is discussed. The relatively slow decay of tunnel magnetoresistance experimen tally observed when P is Cu as a function of the Cu layer thickness is expl ained by considering the particular shape of the Fermi surface in the (111) direction. For other metals, our model predicts a much more rapid decay, i n agreement with experimental observations.