INCOHERENT MAGNETIZATION REVERSAL PROCESS IN DISCONTINUOUS FE50CO50 AG MULTILAYER THIN-FILMS/

The possibility of incoherent magnetization reversal process in anneal ed Fe50Co50/Ag multilayer thin films has been studied. Small magnetore sistance was measured in as-deposited films; however, after annealing above 150 degrees C, the highly mobile Ag atoms form bridges between t he Ag layers, and the magnetoresistance increases, For example, after annealing at 225 degrees C for 30 minutes, the TEM photographs show cl early the crosssection of a discontinuous multilayer structure, the co ercivity is relatively small, and the magnetoresistance reaches its la rgest value. This is explained by the formation of elongated clusters of disk-like ferromagnetic FeCo particles, the exchange coupling betwe en these particles is weak due to the presence of Ag layer between the m. In this case, an incoherent magnetization reversal process is assum ed to be dominant. For samples annealed above 250 degrees C, these dis k-like ferromagnetic particles within a column grow larger due to diff usion. The exchange interaction increase due to the Ag atoms migrating to the bridges between the columns and decreasing the distance betwee n disk-like ferromagnetic particles. The coercivity of the film then i ncreases, and a coherent magnetization reversal process is assumed to become dominant.