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A tunnel junction between a ferromagnet and a normal metal: magnon-assisted contribution to thermopower and conductance

McCann, E and Falko, Vladimir (2004) A tunnel junction between a ferromagnet and a normal metal: magnon-assisted contribution to thermopower and conductance. Journal of Magnetism and Magnetic Materials, 268 (1-2). pp. 123-131. ISSN 0304-8853

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Abstract

We develop a theoretical model of magnon-assisted transport in a mesoscopic tunnel junction between a ferromagnetic metal and a normal (nonmagnetic) metal. The current response to a bias voltage is dominated by the contribution of elastic processes rather than magnon-assisted processes and the degree of spin polarization of the current, parameterized by a function P(Pi(up arrow(down arrow)), Pi(N)), 0less than or equal toPless than or equal to1, depends on the relative sizes of the majority Pi(up arrow) and minority Pi(down arrow) band Fermi surface in the ferromagnet and of the Fermi surface of the normal metal Pi(N). On the other hand, magnon-assisted tunneling gives the dominant contribution to the current response to a temperature difference across the junction. The resulting thermopower is large, Ssimilar to -(k(B)/e)(k(B)T/omega(D))P-3/2(Pi(up arrow(down arrow)), Pi(N)), where the temperature dependent factor (k(B)T/omega(D))(3/2) reflects the fractional change in the net magnetization of the ferromagnet due to thermal magnons at temperature T (Bloch's T-3/2 law) and omega(D) is the magnon Debye energy. (C) 2003 Elsevier B.V. All rights reserved.

Item Type: Article
Journal or Publication Title: Journal of Magnetism and Magnetic Materials
Uncontrolled Keywords: Spin polarized transport ; Ferromagnetism ; Magnon-assisted tunneling ; Thermopower
Subjects: Q Science > QC Physics
Departments: Faculty of Science and Technology > Physics
ID Code: 23933
Deposited By: ep_ss_importer
Deposited On: 24 Feb 2009 09:25
Refereed?: Yes
Published?: Published
Last Modified: 20 Feb 2013 10:03
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/23933

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