Browsing by Author "van Dijk, NH"

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    High/low-moment phase transition in hexagonal Mn-Fe-P-Si compounds
    (American Physical Society, 2012-07-30) Dung, NH; Zhang, L; Ou, ZQ; Zhao, L; van Eijck, L; Mulders, AM; Avdeev, M; Suard, E; van Dijk, NH; Brück, E
    Using high-resolution neutron diffraction measurements for Mn-rich hexagonal Mn-Fe-P-Si compounds, we show that the substitution of Mn for Fe on the 3f sites results in a linear decrease of the Fe/Mn(3f) magnetic moments, while the Mn(3g) magnetic moments remain constant. With increasing temperature, the Mn(3g) magnetic moments show almost no change, while the Fe/Mn(3f) moments decrease quickly when the transition temperature is approached. The reduction of the magnetic moments at the transition temperature and in the high-temperature range is discussed based on changes in interatomic distances and lattice parameters and high-temperature magnetic-susceptibility measurement. © 2012, American Physical Society.
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    Neutron diffraction study on the magnetic structure of Fe2P-based Mn0.66Fe1.29P1-xSix melt-spun ribbons
    (Elsevier Science BV., 2013-08-01) Ou, ZQ; Zhang, L; Dung, NH; van Eijck, L; Mulders, AM; Avdeev, M; van Dijk, NH; Brück, E
    We report on the magnetic and structural properties of Mn0.66Fe1.29P1−xSix melt-spun ribbons with 0.34≤x≤0.42 that are promising candidates for high-temperature magnetocaloric applications. A magnetic moment of up to 4.57 μB/f.u. for x=0.34 indicates high magnetic density in the system, which is certainly advantageous for the magnetocaloric effects. Introducing site disorder at the 3g site by replacing 1/3 of Fe with Mn appears to enhance the magnetic interaction, while the strong magnetoelastic coupling is maintained. This site disorder also shows a stabilizing effect on the hexagonal crystal structure, which is maintained to a high Si content. The moment alignment within the crystallographic unit cell is also affected when the Si content is increased from x=0.34 to 0.42 in the Mn0.66Fe1.29P1−xSix compounds as the canting angle with respect to the c-direction increases. © 2013, Elsevier Ltd.
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    Nucleation kinetics during the solidification of aluminum alloys.
    (Elsevier, 2007-10-15) Iqbal, N; van Dijk, NH; Offerman, SE; Moret, MP; Katgerman, L; Kearley, GJ
    The nucleation kinetics of individual grains during solidification of an aluminium alloy are experimentally investigated by X-ray diffraction at a synchrotron source. The investigated aluminium alloy contained solute titanium along with micrometer size TiB2 particles, which act as substrates for heterogeneous nucleation of aluminium grains during solidification. The nucleation rate of aluminium grains during solidification is measured by different cooling rates ranging from 1 to 40 K/min. The measurements indicate that for the continuous cooling, the nucleation rate strongly decreases with time. The nucleation process is complete for solid fractions below 30% for all cooling rates. The maximum nucleation rate significantly increases with increasing cooling rates. © 2007, Elsevier Ltd.