Inverse tunnel magnetoresistance in epitaxial FeCo/MgO/Fe tunnel junctions patterned by in situ shadow-masks

Abstract Fully epitaxial FeCo/MgO/Fe magnetic tunnel junctions on silicon substrates were fabricated using in situ shadow-masks in an electron-beam deposition system. An inverse tunneling magnetoresistance (TMR) of −39% was observed at 77 K after annealing, which was not obtained in MTJs grown in better vacuum with the same device structure. This inverse TMR is attributed to the oxidation of the FeCo/MgO interface, which provides a negative spin polarization. Our work highlights the importance of interfacial properties on tunneling magnetoresistance and points to a simple processing route to achieve inverse TMR by carefully controlling the oxidation condition of the bottom layer.