Theory of tunneling magnetoresistance of an epitaxial Fe/MgO/Fe(001) junction - art. no. 220403

Calculation of the tunneling magnetoresistance (TMR) of an epitaxial Fe/MgO /Fe(001) junction is reported. The conductances of the junction in its ferr omagnetic and antiferromagnetic configurations are determined without any a pproximations from the real-space Kubo formula using tight-binding bands fi tted to an ab initio band structure of iron and MgO. The calculated optimis tic TMR ratio is in excess of 1000% for an MgO barrier of approximate to 20 atomic planes and the spin polarization of the tunneling current is positi ve for all MgO thicknesses. It is also found that spin-dependent tunneling in an Fe/MgO/Fe(001) junction is not entirely determined by states at the G amma point (k(parallel to) = 0) even for MgO thicknesses as large as approx imate to 20 atomic planes. All these results are explained qualitatively in terms of the Fe majority- and minority-spin surface spectral densities and the complex MgO Fermi surface.