title: Resonant tunneling through electronic trapping states in thin MgO magnetic junctions.
abstract: We report an inelastic electron tunneling spectroscopy study on MgO magnetic junctions with thin barriers (0.85-1.35 nm). Inelastic electron tunneling spectroscopy reveals resonant electronic trapping within the barrier for voltages V>0.15  V. These trapping features are associated with defects in the barrier crystalline structure, as confirmed by high-resolution transmission electron microscopy. Such defects are responsible for resonant tunneling due to energy levels that are formed in the barrier. A model was applied to determine the average location and energy level of the traps, indicating that they are mostly located in the middle of the MgO barrier, in accordance with the high-resolution transmission electron microscopy data and trap-assisted tunneling conductance theory. Evidence of the influence of trapping on the voltage dependence of tunnel magnetoresistance is shown.
authors.affiliation: IFIMUP and IN-Institute of Nanoscience and Nanotechnology, and Departamento de Fisica, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal. jmteixeira@fc.up.pt
authors.forename: J M
authors.initials: JM
authors.lastname: Teixeira
authors.forename: J
authors.initials: J
authors.lastname: Ventura
authors.forename: J P
authors.initials: JP
authors.lastname: Araujo
authors.forename: J B
authors.initials: JB
authors.lastname: Sousa
authors.forename: P
authors.initials: P
authors.lastname: Wisniowski
authors.forename: S
authors.initials: S
authors.lastname: Cardoso
authors.forename: P P
authors.initials: PP
authors.lastname: Freitas