Spin- and symmetry-filtering combined tunnel magnetoresistance through epitaxial MgO/EuS tunnel barriers

Abstract

We created epitaxial magnetic tunnel junctions of FeCo/MgO/EuS on MgO buffered Si (100). Tunnel magnetoresistance reached up to 64% at 4.2 K. An unexpected fast drop of magnetoresistance was recorded for MgO thickness above 1 nm, which is attributed to the forced nonspecular conductance across the EuS conduction band minimum located at the X points, rather than the desired ∆1 conductance centered around the Γ point.