Influence of structural parameters on magnetoresistive properties of CuFeNi melt spun ribbons

The microstructure of Cu80Fe10Ni10 (at%) granular ribbon was investigated by means of atom probe tomography (APT). A granular system is composed of magnetic precipitates embedded in a non-magnetic matrix. In this ribbon, the magnetic precipitates have a diameter smaller than 5 nm in the as-spun state, and their crystallographic structure is very similar to the one of the matrix, which makes it difficult to characterize them using conventional techniques. Those data are of great importance to understand the magnetic and the transport behaviour of these ribbons. Using atom probe tomography, a 3D reconstruction of the microstructure of the as-spun and annealed ribbons was achieved and a precise characterization of the compositions of the two phases and of the composition profile at interfaces was carried out. In the as-spun state the composition of the matrix is Cu89Fe3Ni8, the one of the precipitates is Cu30Fe40Ni30. Upon annealing, the precipitates get enriched in iron. After annealing at 600 °C for 24 h, the measured compositions are close to the one predicted by Thermocalc, with Cu94Fe1Ni5 for the matrix and Cu5Fe64Ni31 for the precipitates.