ELECTRON TRANSMISSION THROUGH ULTRA-THIN METAL LAYERS AND ITS SPIN DEPENDENCE FOR MAGNETIC-STRUCTURES

We present a new set of experiments in which the attenuation of a 'mon oenergetic', possibly spin-polarized, free-electron beam is measured b y direct transmission through an ultra-thin metal layer. The self-supp orted metal target is either a reference gold sample or a ferromagneti c structure. The overall thickness is of the order of 25 nm. The magne tic structure consists of a 1 nm thick cobalt film sandwiched between 21-2 nm thick gold layers, with perpendicular magnetization. Measureme nts are performed throughout a wide energy range, with incident electr on energies 2-1000 eV above the Fermi level. The transmission of the g old layer is found to be substantially higher than that of the magneti c structure. In the latter case, at low energy, close to the clean sur face vacuum level, we find that the majority spin electrons are more e asily transmitted than the minority spin electrons. Cesium deposition on the exit side or on both sides of the target increases the overall transmitted current by almost an order of magnitude. In the case of th e magnetic structure, this also increases the transmission spin asymme try from 16 to about 40%. Such structures appear to be well-suited to the construction of convenient and compact spin-detectors.