The electronic structure and spin-dependent tunneling in epitaxial Fe/MgO/Fe(001) tunnel junctions are studied using first-principles calculations. For small MgO barrier thickness the minority-spin resonant bands at the two interfaces make a significant contribution to the tunneling conductance for the antiparallel magnetization, whereas these bands are, in practice, mismatched by disorder and/or small applied bias for the parallel magnetization. This explains the experimentally observed decrease in tunneling magnetoresistance (TMR) for thin MgO barriers. We predict that a monolayer of Ag epitaxially deposited at the interface between Fe and MgO suppresses tunneling through the interface band and may thus be used to enhance the TMR for thin barriers.
@article{arxiv.cond-mat/0505348,
title = {Effect of interface states on spin-dependent tunneling in Fe/MgO/Fe tunnel junctions},
author = {K. D. Belashchenko and J. Velev and E. Y. Tsymbal},
journal= {arXiv preprint arXiv:cond-mat/0505348},
year = {2007}
}