High tunnel magnetoresistance in epitaxial Fe/MgO/Fe tunnel junctions

Abstract

We report on spin-polarized tunneling in fully epitaxial Fe/MgO/Fe/Co tunnel junctions. By increasing the thickness of the insulating layer ${\mathrm{(t}}_{\mathrm{MgO}}\mathrm{),}$ we have strongly enhanced the tunnel magnetoresistance. Values up to ∼100% at 80 K (∼67% at room temperature) have been observed with $t_{\mathrm{MgO}}\text{=2.5\hspace{0.17em}}\mathrm{nm}.$ This tunnel magnetoresistance ratio, which is much larger than the one predicted by the Jullière’s model, can be understood in the framework of ab initio calculations.