Magnetotransport in epitaxial magnetic tunnel junctions was investigated while varying the density of dislocations in the MgO barrier. Fe-V alloys with variable composition and lattice mismatch with MgO were used as electrodes. The reduction in the dislocation density was probed by reflection high-energy electron diffraction and high-resolution electron microscopy. Spin-resolved photoemission together with first-principles calculations were used to study the Δ bands in the alloys. Although their polarization decreases upon alloying, the tunnel magnetoresistance was enhanced for low V content as a consequence of the better structural coherency. The results demonstrated the direct relationship between the density of dislocations in the epitaxial barrier and the tunnel magnetoresistance amplitude.

Influence of Misfit Dislocations on the Magnetoresistance of MgO-Based Epitaxial Magnetic Tunnel Junctions. F.Bonell, S.Andrieu, C.Tiusan, F.Montaigne, E.Snoeck, B.Belhadji, L.Calmels, F.Bertran, P.Le Fèvre, A.Taleb-Ibrahimi: Physical Review B, 2010, 82[9], 092405