Probing the Size Effect of Co₂FeGa-SiO₂@C Nanocomposite Particles Prepared by a Chemical Approach

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), Fe-57 Mossbauer spectroscopy, and superconducting quantum interference device (SQUID). The superparamagnetic critical size of Co2FeGa Heusler nanoparticles is found to be similar to 17 nm by correlating the TEM derived particle size distribution to the Mossbauer spectroscopy data. The effects of silica supports and carbon coating on the formation of Co2FeGa nanoparticles of various sizes are also discussed