BALLISTIC TRANSPORT AND ELECTRONIC-STRUCTURE

The role of the electronic structure in determining the transport prop erties of ballistic point contacts is studied. The conductance in the ballistic regime is related to simple geometrical projections of the F ermi surface. The essential physics is first clarified for simple mode ls. For real materials the band structure is taken into account using parameter-free local-spin-density approximation calculations. In magne tic metallic multilayers the electronic structure gives rise to a larg e difference in conductance between the parallel and antiparallel conf igurations. For Co/Cu and Fe/Cr multilayers the dependence of the cond uctances on the layer thicknesses and the crystal orientations is inve stigated for the geometries with the current perpendicular, parallel, and at an angle to the interface planes. In spite of the absence of sp in-dependent scattering at defects, the ballistic giant magnetoresista nce effects in the perpendicular geometry can be as large as 120% and 230% in Co/Cu and Fe/Cr multilayers, respectively. [S0163-1829(98)0161 2-8].