Perpendicular transport in Fe/Ge model heterostructures - art. no. 184429

Based on the Kubo-Greenwood equation as formulated for layered systems, an approach is discussed that allows us to separate the resistance of the curr ent leads from that of the region whose resistance we wish to calculate for current perpendicular to the plane of the layers. By applying this approac h to Fe/Ge/Fe model structures related to the parent lattice of bcc Fe we f ind that at least nine layers of the magnetic electrodes should be consider ed as being part of the calculation in order to perform such a separation. With different structures in the Ge spacer. we find that the concentration of vacancies plays a crucial role for the existence of a sizeable magnetore sistance (MR), while the actual structure in the spacer seems to be of less importance. Depending on the type of structure and the number of spacer la yers (in a typical regime of 6-21 layers) the MR for ordered structure vari es between 35% and 45%. Vacancy concentrations of more than 10%. however, w ipe out the MR completely. Interdiffusion at the Fe/Ge interfaces produces very similar effects.