Effects of processing procedures on GMR of Cu-Co alloys

The microstructures of Cu-Co alloys after melt spinning and annealing are investigated by means of metallography and TEM analysis. Experimental results reveal that for melt spun Cu₈₀Co₂₀ alloy, Co-rich phase forms during melt spinning. While Co content exceeds 25 wt%, liquid separation takes place. In 15 wt%-30 wt%Co-C alloys, the spherical precipitation of Co-rich may appear not only on the boundaries but inside the Cu-rich grains during annealing. GMR of melt spun Cu-Co alloys are studied under the different conditions of heat treatment. The results reveal that the variation rate of GMR appearing at low applied field. GMR of melt spun Cu-Co alloys reaches the minimum during a certain time at a fixed annealing temperature because of growing of Co-rich phase and forming of a new modulation structure. When annealing processes very sufficiently, Cu-Co alloys can be magnetized to saturation at 1.0 T.