Microstructure, magnetic properties and giant magnetoresistance of granular Cu-Co alloy

The microstructure in a granular Cu88Co12 alloy was investigated by means o f x-ray diffraction (XRD), a field ion microscope with atom probe (AP-FIM) and a field emission gun-transmission electron microscope (FEG-TEM) with en ergy dispersive x-ray spectroscopy (EDS). Giant magnetoresistance (GMR) and magnetic properties were studied to clarify the relationship between the G MR, magnetic properties and microstructures. The morphology of nanometre-si zed cobalt granules within the grains were directly determined utilizing AP -FIM and FEG-TEM with EDS. Most cobalt granules are spherical and some othe rs are plate-like in shape. GMR was observed in alloys with an average gran ule size ranging from 1.5 to 6 nm in diameter. TEM investigations showed th at larger Go-rich precipitates formed at grain boundaries. The magnetic pro perties of the granular alloy were interpreted using the microstructure inf ormation and the dependence of GMR on magnetization was discussed.