Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 17: Spinabh
ängiger Transport II
MA 17.10: Vortrag
Montag, 7. März 2005, 12:45–13:00, TU H1012
Disorder effects on spin-dependent tunneling — •Michael Wimmer and Klaus Richter — Instut für Theoretische Physik, Universität Regensburg
In contrast to Al2O3-based tunnel junctions recent experiments
on one-crystalline GaAs barriers showed only a very small
tunneling magnetoresistance (TMR) effect,
although band structure considerations predicted a very high
TMR ratio. Some experimental evidence hints at the importance of interfacial
disorder and spin-flips [1,2].
We calculate numerically the effect of interfacial scattering and spin flips
on the TMR using a phenomenological model. Our results show that
disorder decreases the TMR effect significantly and identify the lifting of
the conservation of the parallel momentum as the responsible mechanism.
Surprisingly, allowing spin flips during a scattering event has only little
influence on the TMR ratio.
We further study the influence of the barrier height on the TMR ratio.
The TMR effect of high barriers is found to be more robust against disorder
than low barriers.
References:
S. Kreuzer et al., Appl. Phys. Lett. 80, 4582 (2002)
M. Zenger et al., J. Appl. Phys. 96, 2400 (2004)