Heusler compounds as ternary intermetallic nanoparticles: Co2FeGa

This work describes the preparation of ternary nanoparticles based on the Heusler compound Co2FeGa. Nanoparticles with sizes of about 20 nm were synthesized by reducing a methanol impregnated mixture of CoCl2 · 6H2O, Fe(NO3)3 · 9H2O and Ga(NO3)3 · xH2O after loading on fumed silica. The dried samples were heated under pure H2 gas at 900 0C. The obtained nanoparticles-embedded in silica-were investigated by means of x-ray diffraction (XRD), transmission electron microscopy, temperature dependent magnetometry and Moessbauer spectroscopy. All methods clearly revealed the Heusler-type L21 structure of the nanoparticles. In particular, anomalous XRD data demonstrate the correct composition in addition to the occurrence of the L21 structure. The magnetic moment of the particles is about 5μB at low temperature in good agreement with the value of bulk material. This suggests that the half-metallic properties are conserved even in particles on the 10 nm scale.