Conductance of Mesoscopic Magnetic Systems |
| S. Krompiewski Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland |
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| Theoretical studies of electrical conductance of various nanowires are performed within the framework of a semi-realistic s-d tight-binding model. The presented results concern both homogeneous paramagnetic and ferromagnetic systems as well as trilayers composed of 2 magnetic slabs separated by a nonmagnetic spacer. On the one hand, in the case of the homogeneous systems the attention is focused on conductance quantization, which manifests itself when a contact gets open and conduction decays in a spectacular stepwise way. A new approach is developed by assuming that in the last stage of the breaking of the contact between wires there are fewer and fewer, distributed at random, conduction paths passing through the nanowire cross-section. The corresponding conductances are calculated within the quasiballistic regime, using the Kubo formula and a recursion Green function technique. The results for weak ferromagnets (when both majority and minority bands intersect the Fermi surface) are qualitatively different from those for strong ferromagnets (only the minority bands do), which may explain experimental cumulative conductance histograms of Fe and Ni. On the other hand, giant magnetoresistances of magnetic trilayers are studied for both current-perpendicular-to-plane and current-in-plane geometries. The corresponding magnetoresistances are compared with each other and with the interlayer exchange coupling. |
| DOI: 10.12693/APhysPolA.97.15 PACS numbers: 73.40.Jn, 75.70.-i, 75.70.Pa, 73.23.Ad |