Domain-phase transformations in antiferromagnetically coupled Co/Cu sandwiches

A new type of domain-phase conversion is demonstrated in perfect antiferromagnetically coupled multilayers. The magnetic transformations occurring in polycrystalline Co/Cu/Co sandwiches, exhibiting hardly any coupling defects, have been evidenced by investigating the giant magnetoresistive response along minor loops. The following hypothesis is given for the origin of the transformations. High domain density state, originating in the freedom of the sense of the rotation of the magnetization, occurs when coming from saturation. The domain conversions remain fully reversible above a certain threshold field value. Below this value some domains start to vanish as a consequence of the instabilities that arise from the existence of domain walls with large wall angles. This irreversible process leads to the formation of a new magnetic state, consisting of large domains, where the domain conversions are fully reversible inside a certain field window.