0000000000894307
AUTHOR
Chang-hai Wang
showing 4 related works from this author
Structural and magnetic properties of Fe2CoGa Heusler nanoparticles
2012
Abstract Fe2CoGa Heusler nanoparticles are synthesized by a chemical method. The structure and magnetic properties of Fe2CoGa Heusler nanoparticles are investigated by x-ray diffraction, extended x-ray absorption fine structure and Mössbauer spectroscopy. The crystal structure of Fe2CoGa nanoparticles is described by the X-type structure (prototype: Li2AgSb). Magnetic measurements reveal the presence of small Fe2CoGa nanoparticles and lower magnetic moments compared with the theoretically predicted values.
Probing the Size Effect of Co2FeGa-SiO2@C Nanocomposite Particles Prepared by a Chemical Approach
2010
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 Mossbauer 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 par…
Pressure-restored superconductivity in Cu-substituted FeSe
2011
Copper doping of FeSe destroys its superconductivity at ambient pressure, even at low doping levels. Here we report the pressure-dependent transport and structural properties of Fe${}_{1.01\ensuremath{-}x}$Cu${}_{x}$Se with 3$%$ and 4$%$ Cu doping and find that the superconductivity is restored. Metallic resistivity behavior, absent in Cu-doped FeSe, is also restored. At the low pressure of 1.5 GPa, superconductivity is seen at 6 K for 4$%$ Cu doping, somewhat lower than the 8 K ${T}_{c}$ of undoped FeSe. ${T}_{c}$ reaches its maximum of 31.3 K at 7.8 GPa, lower than the maximum superconducting temperature in the undoped material under pressure (${T}_{c}$ max of 37 K) but still very high. X…
Heusler compounds as ternary intermetallic nanoparticles: Co2FeGa
2009
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??C. The obtained nanoparticles?embedded in silica?were investigated by means of x-ray diffraction (XRD), transmission electron microscopy, temperature dependent magnetometry and M??bauer spectroscopy. All methods clearly revealed the Heusler-type L21 structure of the nanoparticles. In particular, anomalous XRD data demonstrate the correct composition in addi…