We study transport properties of nano-scale wires connected to ferromagnetic semi-infinite electrodes in the ballistic regime. Systems with different geometries are considered. Our method is based on recursive Green's function technique. We fully deal with atomistic structure of the whole system, treating both the nano-wire and the electrodes on equal footing. The results include the transmission, with parallel and antiparallel magnetization in the electrodes, and giant magnetoresistance (GMR) vs. energy. The influence of the magnetic polarization, coupling between the nano-wire and the electrodes as well as the geometry of the device on transport properties are discussed. We emphasize the shape dependent effects and take into account also imperfect structures with some atoms removed from the central region. In addition to evolution from conductance quantization to resonant tunneling regime (upon changing the hopping parameter), it has been found that with increasing polarization other features appear due to decreasing overlap between surface density of states of propagating modes. (c) 2006 WLLEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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