Spin-dependent tunneling spectroscopy for interface characterization of epitaxial Fe/MgO/Fe magnetic tunnel junctions...

Low-voltage spin-dependent tunneling spectroscopy of an epitaxial Fe/MgO/Fe magnetic tunnel junction is measured and compared to first-principles calculation of the tunneling conductance. The measured dynamic conductance ($dI/dV$) in the parallel configuration shows distinct asymmetric features as a function of the bias voltage $V$. The peaks are independent of barrier thickness, magnetic field, and temperature. From the first-principles calculation, we identify the positive and negative bias spectra corresponding to different types of Fe/MgO interfaces. Tunneling spectroscopy thus can be used as a powerful tool for interface characterization.