Spin- and Symmetry-Filtering Combined Tunnel Magnetoresistance through   Epitaxial MgO/EuS Tunnel Barriers
  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 point, rather than the desired Delta_1 conductance centered around the Gamma point. 
Zhiwei Gao, Yihang Yang, Fen Liu, Qian Xue, Guo-Xing Miao
cond-mat.mtrl-sci