Absence of tunnel magnetoresistance in Sr2FeMoO6-based magnetic tunnel junctions

X-ray magnetic circular dichroism (XMCD) and X-ray photoemission spectroscopy (XPS) are performed on a Sr2FeMoO6 thin film to explain the absence of tunnel magnetoresistance in a fully epitaxial magnetic tunnel junction integrating a Sr2FeMoO6 electrode, despite the high quality of the deposition. Although superconducting quantum interference device (SQUID) measurements indicate a room temperature magnetization of 3.2 μB/formula unit, the surface magnetic moment deduced from XMCD is anomalously weak. This is consistent with a lack of Fe at the surface of Sr2FeMoO6 as observed by XPS leading to an absence of tunnel magnetoresistance.