摘要
In this contribution, we report the chemical synthesis of carbon coated, silica supported Co 2 FeGa (Co 2 FeGa-SiO 2 @C) nanocomposite particles. The particle size of Co 2 FeGa particles can be tuned by varying the amount of silica supports. The dependences of the crystal structure and magnetic properties on particle size have been investigated by synchrotron radiation based X-ray diffraction (XRD), X-ray absorption fine structure (XAFS) spectroscopy, transmission electron microscope (TEM), 57 Fe Mössbauer spectroscopy, and superconducting quantum interference device (SQUID). The superparamagnetic critical size of Co 2 FeGa Heusler nanoparticles is found to be ∼17 nm by correlating the TEM derived particle size distribution to the Mössbauer spectroscopy data. The effects of silica supports and carbon coating on the formation of Co 2 FeGa nanoparticles of various sizes are also discussed. © 2010 American Chemical Society.