Nanoparticle morphology in a granular Cu–Co alloy with giant magnetoresistance

The morphology of nanometer-sized cobalt granules in a granular Cu88Co12 alloy was directly determined utilizing an atom probe-field ion microscope. The granules are spherical in shape, and exhibit a size distribution. Giant magnetoresistance (GMR) was observed in alloys with an average granule size ranging from 1.5 to 6 nm in diameter. A well-known theoretical model of general GMR behavior in magnetic granular systems was confirmed based on measurement of size distribution of the granules.