Transport properties of discontinuous Co/sub 80/Fe/sub 20//Al/sub 2/O/sub 3/ multilayers, prepared by ion beam sputtering

Ion beam sputtered Co/sub 80/Fe/sub 20/(t)/Al/sub 2/O/sub 3/ (30 /spl Aring/) multilayers were obtained. The Co/sub 80/Fe/sub 20/ layers become discontinuous for nominal thickness t/spl les/18 /spl Aring/. Tunnel magnetoresistance was measured in CIP and CPP geometries, reaching up to 6.5% at room temperature and 11% at 15 K, for as-deposited films in CIP geometry. The temperature dependence of MR was found quite different for the two geometries: fairly strong in the CIP case and almost absent in the CPP geometry. A model is proposed to explain these large differences in behavior.