Volume 78, Number 1, April 2007
Article Number 17003
Number of page(s) 4
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 14 March 2007
EPL, 78 (2007) 17003
DOI: 10.1209/0295-5075/78/17003

Equilibrium spin transport in the ferromagnet/ferromagnet tunnelling junction

Y. G. Shen and Z. H. Yang

Department of Physics, Southeast University - Nanjing 210096, PRC

received 23 November 2006; accepted in final form 14 February 2007; published April 2007
published online 14 March 2007

We study theoretically the equilibrium spin current (ESC) flowing through a ferromagnet/insulator barrier/ferromagnet (FM/I/FM) tunnelling junction in a lattice model. By using the Keldysh Green's function technique, we obtained an exact result of ESC based on the model. At the low transmission barrier limit, the exact solution can approximate the well-known linear response result that ESC comes from the exchange coupling between two magnetizations, ${\bf J}_{s}\sim {\bf h}_{L}\times {\bf h}_{R}$; whereas at the case of zero barrier between two FMs the ESC will vanish, which is attributed to a quantum mechanics effect that the electron reflection at the barrier (interface) is crucial for ESC formation in the junction. An analytic relation between ESC and the system conductance was found at the case of the weak magnetization and strong barrier.

73.23.-b - Electronic transport in mesoscopic systems.
72.25.Dc - Spin polarized transport in semiconductors.
71.70.Ej - Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect.

© Europhysics Letters Association 2007