Coercivity and magnetization process versus dipolar coupling in Ni80Fe20/Cu/Co/Cu spin valves

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Abstract
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 vicinity of the free surface has allowed for a detailed study of the magnetization process of the constitutive layers of one period of a ‘‘hard–soft’’-type spin valve. The domain distribution and magnetization fluctuations within domains have been monitored by Kerr microscopy. The experiments point to a strong influence of dipolar coupling on the properties 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 the NiFe layer appear most likely linked to fluctuations of low amplitude occurring in the Co layer in the vicinity of the NiFe coercive field.