Spin-dependent tunneling spectroscopy in single-crystal Fe/MgO/Fe tunnel junctions

We report a detailed spin-dependent tunneling spectroscopy in single-crystal Fe(001)∕MgO(001)∕Fe(001) magnetic tunnel junctions (MTJs) that show a giant tunnel magnetoresistance effect. Spectra for antiparallel magnetic configurations show asymmetry because of extrinsic electron scatterings caused by structural defects at the barrier/electrode interfaces. Surprisingly, spectra for parallel magnetic configurations exhibit a complex oscillatory structure that has never been observed in conventional MTJs with an aluminum-oxide tunnel barrier. The complex spectra reflect the tunneling process via interface resonant states. These results provide some information that helps to elucidate the physics of spin-dependent electron tunneling and to further enhance magnetoresistance.

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