| Issue |
Europhys. Lett.
Volume 50, Number 2, April II 2000
|
|
|---|---|---|
| Page(s) | 271 - 277 | |
| Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
| DOI | https://doi.org/10.1209/epl/i2000-00265-7 | |
| Published online | 01 September 2002 | |
Unified approach to the tunnel magnetoresistance and the non-equilibrium exchange interaction
University of Oxford, Department of Physics,
Theoretical Physics 1 Keble Road, Oxford OX1 3NP, UK
Received:
25
October
1999
Accepted:
10
February
2000
The tunnel magnetoresistance and its connection to the interlayer
exchange interaction is studied in ferromagnet-insulator-ferromagnet
junctions. Building on the non-equilibrium Keldysh formalism, we
include a contact interaction between localized spins and conduction
electrons and derive an expression for the tunnel current that depends
on the magnetization of the layers as 
in correspondence with the exchange coupling. From this
expression we also obtain a formula for the tunnel
magnetoresistance. At low bias and for systems where one can neglect
size-quantization effects Julliere's formula is rederived. The
temperature dependence of the dynamical parameters arises from the
system of localized spins, its interaction with the conduction
electrons, and the thermal reservoirs.
PACS: 75.70.Pa – Giant magnetoresistance / 73.40.Rw – Metal-insulator-metal structures / 75.10.-b – General theory and models of magnetic ordering
© EDP Sciences, 2000
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