Shot noise in magnetic tunnel junctions: evidence for sequential tunneling.
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.
Guerrero
R
R
Departamento de Fisica de la Materia Condensada, C-III, Universidad Autonoma de Madrid, 28049 Madrid, Spain.
Aliev
F G
FG
Tserkovnyak
Y
Y
Santos
T S
TS
Moodera
J S
JS