Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 23: Nanoelectronics II - Spintronics and Magnetotransport
TT 23.10: Vortrag
Donnerstag, 29. März 2007, 12:00–12:15, H19
Theoretical study of the conductance of ferromagnetic atomic-sized contacts — •M. Häfner1,2, J. Viljas1,2, D. Frustaglia3, F. Pauly1,2, M. Dreher4, P. Nielaba4, and J. C. Cuevas5,1,2 — 1Institut für Theoretische Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe — 2FZ Karlsruhe, Institut für Nanotechnologie, D-76021 Karlsruhe — 3NEST-CNR-INFM & SNS, I-56126 Pisa — 4Fachbereich Physik, Universität Konstanz, D-78457 Konstanz — 5Universidad Autónoma de Madrid, E-28049 Madrid
Different experiments on the transport through atomic-sized contacts made of ferromagnetic materials have produced contradictory results such as the observation of half-integer conductance quantization. We have studied theoretically the conductance of ideal atomic contact geometries of the ferromagnetic 3d materials Fe, Co, and Ni using a realistic tight-binding model. Our analysis [1] shows that in the absence of magnetic domains, the d bands of these transition metals play a key role in the electrical conduction. In the contact regime this fact leads to the following consequences: (i) there are partially open conduction channels and therefore conductance quantization is not expected, (ii) the conductance of the last plateau is typically above G0=2e2/h, (iii) both spin species contribute to the transport and thus there is in general no full current polarization, and (iv) both the value of the conductance and the current polarization are very sensitive to the contact geometry and to disorder. In the tunneling regime we find that a strong current polarization can be achieved.
[1] M. Häfner et al., cond-mat/0608132