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.