Sonochemical preparation of nanosized amorphous Fe-Ni alloys

Nanosized amorphous alloy powders of Fe₂₀Ni₈₀, Fe₄₀Ni₆₀, and Fe₆₀Ni₄₀ were prepared by sonochemical decomposition of solutions of volatile organic precursors, Fe(CO)₅ and Ni(CO)₄ in decalin, under an argon pressure of 100 to 150 kPa at 273 K. Magnetic susceptibility of Fe₄₀Ni₆₀ and Fe₆₀Ni₄₀ indicates blocking temperatures of 35 K and a magnetic particle size of about 6 nm. Thermogravimetric measurements of Fe₂₀Ni₈₀ give Curie temperatures of 322 °C for amorphous and 550 °C for crystallized forms. Differential scanning calorimetry exhibits an endothermic transition at 335 °C from a combination of the magnetic phase transition and alloy crystallization. The Mössbauer spectrum of crystallized Fe₂₀Ni₈₀ shows a sextet pattern with a hyperfine field of 25.04T.