Enhanced tunnel magnetoresistance in magnetic tunnel junctions with a cubic Mg-Al-O barrier

摘要

The spinel MgAl_2O_4 (spinel structure) is advantageous to a tunnel barrier of magnetic tunnel junctions (MTJs) because of its nondeliquescency and its small lattice mismatch with typical bcc-Fe(Co) alloys and Co-based Heusler alloys (～ 1%). Therefore an achievement of perfect lattice-matched structure with defect-free barrier interfaces is expected in MgAl_2O_4-based MTJs. We recently reported a relatively large tunnel magnetoresistance (TMR) of 117% at room temperature (RT) and 165% at 16 K in an epitaxial Fe/spinel MgAl_2O_4/Fe(001) MTJ. However the obtained TMR was still small for practical applications. In this study we fabricated CoFe/MgAl-O_x/CoFe MTJs and achieved a larger TMR (over 300% at RT) using an off-stoichiometric Mg-Al-O barrier.