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APS » Journals » Phys. Rev. Lett. » Volume 97 » Issue 26
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Phys. Rev. Lett. 97, 266602 (2006) [4 pages]

Shot Noise in Magnetic Tunnel Junctions: Evidence for Sequential Tunneling

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R. Guerrero1, F. G. Aliev1, Y. Tserkovnyak2, T. S. Santos3, and J. S. Moodera3
1Departamento de Fisica de la Materia Condensada, C-III, Universidad Autonoma de Madrid, 28049, Madrid, Spain
2Lyman Laboratory of Physics, Harvard University, Cambridge, Massachusetts 02138, USA and Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
3Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

Received 21 February 2006; published 28 December 2006

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.

© 2006 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.97.266602
DOI:
10.1103/PhysRevLett.97.266602
PACS:
72.25.Mk, 73.40.Gk, 75.47.−m
 
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