COERCIVITY AND MAGNETIZATION PROCESS VERSUS DIPOLAR COUPLING IN NI80FE20 CU/CO/CU/

The elaboration of four different sample types, namely, isolated NiFe or Co layers in their Cu environment and full, exchange decoupled, [Cu /NiFe/Cu/Co/Cu] periods with either the Co or NiFe layers in the vicin ity of the free surface has allowed for a detailed study of the magnet ization process of the constitutive layers of one period of a ''hard-s oft''-type spin valve. The domain distribution and magnetization fluct uations within domains have been monitored by Kerr microscopy. The exp eriments point to a strong influence of dipolar coupling on the proper ties of the soft permalloy layer, with a dramatic increase of the NiFe film coercive field with respect to the corresponding quantity in an isolated NiFe layer. The macromagnetization fluctuations detected in t he NiFe layer appear most likely linked to fluctuations of low amplitu de occurring in the Co layer in the vicinity of the NiFe coercive fiel d.