The irreversibilities in antiferromagnetically coupled Co/Cu/Co sandwiches prepared by dc-magnetron sputtering are shown to strongly depend on the magnetic history of the samples. The irreversibilities, evidenced by the analysis of the giant magnetoresistance and magnetization response along minor loops, are attributed to domain-phase transformations. A method is given for estimating the amount of remanence in the Co/Cu/Co sandwich, based on the analysis of the giant magnetoresistive response. The perfect antiferromagnetic alignment at zero field is attributed to the formation of a magnetic state with relative large domains. The small amount of remanence detected in some samples is ascribed to the persistence at zero field of a significant density of domain walls.

• Received 6 August 1999

DOI:https://doi.org/10.1103/PhysRevB.62.3917