MICROSTRUCTURAL ORIGIN OF GIANT MAGNETORESISTANCE IN A NEW SENSOR STRUCTURE-BASED ON NIFE AG DISCONTINUOUS MULTILAYER THIN-FILMS/

The origin of giant magnetoresistance (GMR) in a new sensor structure incorporating discontinuous multilayers (DML) of NiFe thin films separ ated by Ag interlayers is elucidated by means of x-ray diffraction, x- ray reflectivity, and cross-section transmission electron microscopy. It is shown that the observed magnetoresistance, approximately 4%-6% i n fields on the order of 5-10 Oe at 25-degrees-C, is associated with t he breakup upon annealing of the initially dense, columnar superlattic e structure into discontinuous multilayers of NiFe due to highly mobil e Ag forming Ag bridges between the Ag layers. This observation suppor ts a micromagnetic model for these structures that is based on the con cept of initially large ferromagnetic domains in the as-deposited NiFe structure, exhibiting negligible GMR, breaking up into discontinuous layers, exhibiting an appreciable GMR, with antiferromagnetic ordering across the Ag interlayers.