Observation of domain dynamics in giant magnetoresistive Co–Cu-based polycrystalline multilayers

A high resolution interference-contrast colloid technique has been used to investigate domain dynamics associated with the antiferromagnetic (AF)⇔ferromagnetic (F) magnetization reversal processes in polycrystalline Co–Cu-based magnetic multilayers exhibiting giant magnetoresistance. The magnetization reversal was found to be local and nonuniform in nature: within each grain reversal occurs by nucleation of one or more reversed domains at its grain boundary, and different grains require different critical applied field values for wall nucleation, and their subsequent motion. Significantly, the domain dynamics associated with F⇒AF reversal were found to have different characteristics in comparison with the AF⇒F magnetization reversal. These results indicate asymmetrical giant magnetoresistance loop characteristics at the mesoscopic scale.