Browsing by Author "Yang, CC"

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    Effects of oxygen deficiency on the magnetic ordering of Mn in Tb0.9Na0.1MnO2.9
    (Institute of Physics, 2008-03-12) Yang, CC; Wu, CM; Li, WH; Chan, TS; Liu, RS; Chen, YY; Avdeev, M
    Monovalent Na+ ions have been incorporated into a multiferroic TbMnO3 compound. Structural studies, using high-resolution neutron diffraction patterns, show that monovalent Na+-doping results in a noticeable oxygen deficiency in the compound. The alternations in crystalline and magnetic structures due to oxygen deficiency are investigated by neutron diffraction and magnetic susceptibility measurements. Na-doping turns the modulated incommensurate Mn spin structure, observed for the parent compound, into a simple commensurate one. The observed magnetic diffraction patterns agree very well with that calculated assuming a D-type arrangement for the Mn spins, with the moments pointing along the c-axis direction. No significant alternation in the ordering temperature of the Mn moments is found. © 2008, Institute of Physics
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    SIKA - a new triple-axis-spectrometer for cold neutrons
    (Australian Institute of Physics, 2006-12-05) Li, WH; Yang, CC; Vorderwisch, P
    The new OPAL reactor at ANSTO will be among the world-top research reactors equipped with a cold neutron source. A cold-neutron triple-axis-spectrometer named SIKA, designed and to be operated by a research team from Taiwan, will extend the day-one instrumentation at OPAL especially for measurements of low-energy excitations in single crystals (phonon or magnon dispersion relations) or, in an elastic mode, of weak superstructure reflections. Modern applications of such a spectrometer are magnetic-field driven quantum-phase transitions and magnetic-field induced ordering phenomena in high TC superconductors. Whereas a high resolution of such a spectrometer is inherently given by the use of cold neutrons, a high intensity of measured signals will be obtained using focusing methods. An option to work with polarised neutrons will also be available. We describe the conceptual design of SIKA and its expected performance, both based on MonteCarlo simulations using the codes McStas and MCNP. Finally we compare SIKA with other state-of-the-art cold-neutron triple-axis-spectrometers.