  Bulk nanocrystalline materials of small and medium ferromagnetic content were
produced using severe plastic deformation by high-pressure torsion at
roomtemperature. Giant magnetoresistive behavior was found for as deformed
materials, which was further improved by adjusting the microstructure with
thermal treatments. The adequate range of annealing temperatures was assessed
with in-situ synchrotron diffraction measurements. Thermally treated CuCo
materials show larger giant magnetoresistance after annealing for 1 h at 300C,
while for CuFe this annealing temperature is too high and decreases the
magnetoresistive properties. The improvement of magnetoresistivity by thermal
treatments is discussed with respect to the microstructural evolution as
observed by electron microscopy and ex situ synchrotron diffraction
measurements.
