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Effect of interface states on spin-dependent tunneling in Fe ∕ Mg O ∕ Fe tunnel junctions

2005; American Physical Society; Volume: 72; Issue: 14 Linguagem: Inglês

10.1103/physrevb.72.140404

1550-235X

K. D. Belashchenko, Julian Velev, Evgeny Y. Tsymbal,

Magnetic Properties and Synthesis of Ferrites

The electronic structure and spin-dependent tunneling in epitaxial $\mathrm{Fe}∕\mathrm{Mg}\mathrm{O}∕\mathrm{Fe}(001)$ 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.