DEPENDENCE OF GIANT MAGNETORESISTANCE ON GRAIN-SIZE IN CO CU MULTILAYERS/

The effect of grain size on the magnetoresistance (MR) of Co/Cu multil ayers fabricated by dc magnetron sputtering has been studied using Co/ Cu multilayers grown with identical Co and Cu thicknesses but differen t grain sizes. These multilayers were selectively fabricated by growin g with and without a Cu underlayer: grain-to-grain epitaxy from the bu ffer layer to the superlattice in the former facilitated control of th e multilayer grain structure. The MR was found to increase with increa sing grain size, with the difference being larger at low temperature. The enhancement of MR is attributed to an increased electron mean free path leading to sampling of more antiferromagnetically coupled layers .