DOMAIN OBSERVATIONS ON NIFECO CU/NIFECO-SANDWICHES FOR GIANT MAGNETORESISTIVE SENSORS/

We prepared NiFeCo-Cu-NiFeCo GMR senses structures with crossed anisot ropy. The ferromagnetic layers are weekly coupled. The measured GMR ra tio is about 1.2%-smaller than the ratio derived from measurements on similar spin-valve structures. To explain the poor performance we stud ied the domains in the coupled ferromagnetic layers by Kerr microscopy . The magnetization processes ape strongly influenced by the remaining weak ferromagnetic coupling and the occurrence of compensated wall st ructures. These irregularities lead to reduced GMR ratios. Also the fo rmation of 360 degrees-walls cars be observed.