Nanostructure of Giant Magnetoresistance Heterogeneous Alloys Ni0.20Ag0.80 After Annealing

Heterogeneous alloys N 0.20 A g0.80 presenting giant magnetoresistance properties, have been studied by Total Electron Yield X-ray absorption spectroscopy at liquid nitrogen temperature at the Ni K edge from as-deposited to annealed stages. Up to 150°C annealing, the Ni atoms are mainly in small poorly ordered agglomerates and the local Ni atomic environment is very stable and disordered. Up to 250°C annealing, some Ni atoms occupy substitutional sites in the Ag matrix and 40 to 50 % of the Ni nearest neighbors are Ag atoms. After annealing at 400°C during 10 mn, the nanostructures evolve towards larger, more compact and well ordered granules. The Ni-Ni distance varies from 0.246 to 0.248 nm as the annealing temperature increases indicating that the small agglomerates are under strain in the Ag matrix.