INFLUENCE OF ANNEALING CONDITION ON GIANT MAGNETORESISTANCE OF FECO-CU GRANULAR FILMS

FeCo-Cu granular films were prepared by DC magnetron sputtering using mixed targets. Two kinds of annealing procedures named 'isochronous an nealing' and 'cumulative isothermal annealing' were used to promote th e grain growth or phase segregation of as-deposited films. The influen ce of annealing condition on magnetoresistance has been investigated s ystematically for the films with optimal composition. It is found that for the films with same composition, the cumulative isothermal anneal ed samples have larger giant magnetoresistance (GMR) in comparison wit h the isochronous annealed ones. Transmission Electron Microscope stud y shows that the isochronous annealing promotes the grain growth a lit tle excessively sometimes which is not in favor of the GMR improvement . The shea-time isothermal annealing at a modest higher temperature, h owever, limits the grain growth due to the very short annealing time. By repeating this annealing step several times, more and homogenous fi ne particles are obtained, which leads to the larger GMR. Therefore, a cumulative isothermal annealing at an optimal temperature is recommen ded. (C) 1997 Elsevier Science S.A.