Investigation of cobalt–iron alloy nanoparticles in silica matrix by X-ray diffraction and Mössbauer spectroscopy

Nanocrystals of Co100−xFex with different nominal iron content (x=50, 70, 100) embedded in amorphous silica matrix were prepared by the sol–gel method and thermal treatment in hydrogen atmosphere. Different salts (acetates and nitrates) were used as metal precursors. The samples were characterized by X-ray diffraction and Mössbauer spectroscopy in order to verify the formation of the Fe–Co alloy and investigate its structure and composition. XRD patterns only for acetate samples exhibit peaks belonging to a body centered cubic phase, expected for the Fe–Co alloy at the investigated compositions, and also the lattice parameter values confirm the alloy formation. The average particle size obtained by the Warren–Averbach analysis turned out 9.6(5) nm. In agreement with these results, Mössbauer spectra show the formation of an ordered component with isomer shift and hyperfine fields typical of the Fe–Co alloy only for acetate samples.