Browsing by Author "Fitzsimmons, MR"

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    Dynamical theory calculations of spin-echo resolved grazing-incidence scattering from a diffraction grating
    (Wiley-Blackwell, 2010-06-01) Ashkar, R; Stonaha, P; Washington, AL; Shah, VR; Fitzsimmons, MR; Maranville, B; Majkrzak, CF; Lee, WT; Schaich, WL; Pynn, R
    Neutrons scattered or reflected from a diffraction grating are subject to a periodic potential analogous to the potential experienced by electrons within a crystal. Hence, the wavefunction of the neutrons can be expanded in terms of Bloch waves and a dynamical theory can be applied to interpret the scattering phenomenon. In this paper, a dynamical theory is used to calculate the results of neutron spin-echo resolved grazing-incidence scattering (SERGIS) from a silicon diffraction grating with a rectangular profile. The calculations are compared with SERGIS measurements made on the same grating at two neutron sources: a pulsed source and a continuous wave source. In both cases, the spin-echo polarization, studied as a function of the spin-echo length, peaks at integer multiples of the grating period but there are some differences between the two sets of data. The dynamical theory explains the differences and gives a good account of both sets of results. © 2010, Wiley-Blackwell.
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    Neutron depolarisation studies on Pd-Ni-Fe-P alloy
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Yu, DH; Robinson, RA; Fitzsimmons, MR; Woodward, RC; Gilbert, EP
    Magnetic metallic glasses have enormous technological importance in, for example, magnetic recording, magnetic refrigeration and the construction of electrical transformers and motors. Traditionally these amorphous materials were prepared by melt spinning to form ribbons. Bulk magnetic metallic glasses based on the quaternary alloy Pd-Ni-Fe-P exhibit interesting phase behaviour depending on temperature and applied magnetic field. For the alloy of Pd40Ni22.5Fe17.5P20, paramagnetic, superparamagnetic, ferromagnetic and spin glass regions are all evidenced (Shen et al. J. Appl. Phys. 85, 4110, (1999)). It is proposed that the complex phase transitions may be due to the frustration caused by competing interactions between magnetic clusters presented in the material. We will present preliminary findings from neutron depolarization studies on the alloy of Pd40Ni22.5Fe17.5P20 as a function of temperature (RT to 10K) and applied magnetic field up to 11T. © The Authors
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    Neutron depolarization studies of Pd-Ni-Fe-P alloy
    (Elsevier, 2007-07-15) Yu, DH; Fitzsimmons, MR; Gilbert, EP; Woodward, RC; Kilcoyne, SH; Robinson, RA
    Bulk metallic glasses based on the quaternary alloy Pd-Ni-Fe-P exhibit interesting phase behavior depending on temperature and applied magnetic field. Previous work has suggested that a range of magnetic phases, including paramagnetic, superparamagnetic, ferromagnetic and spin glass, can be observed in this system. We have applied one-dimensional neutron depolarization to explore the correlation of magnetic moments in Pd40M22.5Fe17.5P20 alloy as a function of temperature and applied magnetic field. The results provided evidence for correlation lengths of similar to 200A. The nature of the correlations and the formation mechanism of the induced ferromagnetic phase are discussed. © 2007, Elsevier Ltd.