文摘
In this contribution, we report the chemical synthesis of carbon coated, silica supported Co2FeGa (Co2FeGa-SiO2@C) nanocomposite particles. The particle size of Co2FeGa 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), 57Fe Mssbauer spectroscopy, and superconducting quantum interference device (SQUID). The superparamagnetic critical size of Co2FeGa Heusler nanoparticles is found to be 17 nm by correlating the TEM derived particle size distribution to the Mssbauer spectroscopy data. The effects of silica supports and carbon coating on the formation of Co2FeGa nanoparticles of various sizes are also discussed.