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)