Eur. Phys. J. B 82, 319-327 (2011)
https://doi.org/10.1140/epjb/e2011-20271-2

Nonmonotonic inelastic tunneling spectra due to surface spin excitations in ferromagnetic junctions

¹ Institute for Theoretical Physics, Regensburg University, 93040 Regensburg, Germany
² Institute for Theoretical Physics and Astrophysics, Würzburg University, Am Hubland, 97074 Würzburg, Germany

Corresponding author: ^a Grigory.Tkachov@physik.uni-wuerzburg.de

Received: 5 April 2011
Revised: 3 July 2011
Published online: 12 August 2011

Abstract

The paper addresses inelastic spin-flip tunneling accompanied by surface spin excitations (magnons) in ferromagnetic junctions. The inelastic tunneling current is proportional to the magnon density of states which is energy-independent for the surface waves and, for this reason, cannot account for the bias-voltage dependence of the observed inelastic tunneling spectra. This paper shows that the bias-voltage dependence of the tunneling spectra can arise from the tunneling matrix elements of the electron-magnon interaction. These matrix elements are derived from the Coulomb exchange interaction using the itinerant-electron model of magnon-assisted tunneling. The results for the inelastic tunneling spectra, based on the nonequilibrium Green's function calculations, are presented for both parallel and antiparallel magnetizations in the ferromagnetic leads.