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Article Dans Une Revue Philosophical Magazine Année : 2008

A transmission electron microscopy and X-Ray diffraction study of microstructural evolution in magnetoresistive Cu-Fe-Ni ribbons

Résumé

The evolution of the microstructure of a granular Cu80Fe10Ni10 (at%) melt spun ribbon is studied by means of transmission electron microscopy (TEM), energy filtered transmission electron microscopy (EFTEM) and X-Ray Diffraction. This system is interesting since large giant magnetoresistance (GMR) values have been measured for this composition. We have shown the presence of two face-centered cubic phases, an (Fe,Ni)-rich phase and a Cu-rich phase. The lattice parameters of those two phases are rather close and no diffraction or elastic contrast acts to evidence the two phases in TEM bright field mode. With EFTEM imaging, we have shown the presence of a fine scale (Fe,Ni)-rich precipitation, inside the Cu-rich fcc matrix. The precipitates are 2-4 nm large in the as-spun state, and 4-6 nm large after an annealing treatment of 2 hours at 400°C. The lattice parameter of the Cu-rich phase in the as-spun sample is 0.3608 nm, and that of the (Fe,Ni)-rich phase is 0.3610 nm. After a 24 hours treatment at 600°C, the mean diameter of the particle is 20 nm and the lattice parameter of the (Fe,Ni)-rich phase has decreased to 0.3600 nm while that of the Cu-rich phase has increased to 0.3613 nm, which is constistent with a segregation of Fe and Ni in the precipitates. The composition and volume fraction of the two phases measured for this annealed sample are in good agreement with the Thermocalc® predictions.

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Dates et versions

hal-00513899 , version 1 (01-09-2010)

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Sophie Cazottes, Guillaume Yangshu. Wang, Abdeslem Fnidiki, Dany Lemarchand, Pierre Olivier Renault, et al.. A transmission electron microscopy and X-Ray diffraction study of microstructural evolution in magnetoresistive Cu-Fe-Ni ribbons. Philosophical Magazine, 2008, 88 (09), pp.1345-1356. ⟨10.1080/14786430802136234⟩. ⟨hal-00513899⟩
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