title: Shot noise in magnetic tunnel junctions: evidence for sequential tunneling.
abstract: We report the experimental observation of sub-Poissonian shot noise in single magnetic tunnel junctions, indicating the importance of tunneling via impurity levels inside the tunnel barrier. For junctions with weak zero-bias anomaly in conductance, the Fano factor (normalized shot noise) depends on the magnetic configuration being enhanced for antiparallel alignment of the ferromagnetic electrodes. We propose a model of sequential tunneling through nonmagnetic and paramagnetic impurity levels inside the tunnel barrier to qualitatively explain the observations.
authors.affiliation: Departamento de Fisica de la Materia Condensada, C-III, Universidad Autonoma de Madrid, 28049 Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Guerrero
authors.forename: F G
authors.initials: FG
authors.lastname: Aliev
authors.forename: Y
authors.initials: Y
authors.lastname: Tserkovnyak
authors.forename: T S
authors.initials: TS
authors.lastname: Santos
authors.forename: J S
authors.initials: JS
authors.lastname: Moodera