Structural investigation of icosahedral Pd58.8U20.6Si20.6

The structure factors of the amorphous, icosahedral and crystalline Pd_58.8U_20.6Si_20.6 were measured with X-rays and neutrons. By comparing the radial distribution functions of the three phases, we find a similar short range order in the amorphous and icosahedral phase, but a different atomic arrangement in the crystalline phase. A magnetic long range order observed in the crystalline material is absent in the icosahedral phase.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday     

Total dynamic structure factor of icosahedral and As-quenched and relaxed glassy Pd58.8Si20.6U20.6 measured at 296 K

The total dynamic structure factorsS(Q, ) of icosahedral, glassy Pd_58.8Si_20.6U_20.6, and the crystallized sample have been determined at room temperature using inelastic scattering of cold neutrons (IN6 of ILL). In contrast to the static structure factorS(Q), where the long range bond orientational order (BOO) leads to pronounced diffraction peaks with finite half width, the dynamic structure factor shows little or no influence of the long range BOO on the atomic dynamics of icosahedral PdSiU in the range of frequencies (0.525 meV) and momentum transfers Q(5Q30 nm^–1 for inelastic scattering) investigated here. The wavelength-dependence of the atomic dynamics of icosahedral PdSiU is very similar to that of the metallic glass and is different from that of the crystallized sample. As for glassy PdSiU no well defined vibrational collective excitations are found as peaks in the inelastic part ofS(Q, ) of the icosahedral sample,-quite in contrast to theoretical expectations and to the dispersions of pronounced excitations determined under identical experimental conditions fromS(Q, ) of the crystallized sample. On structural relaxation of the metallic glass Pd_58.8Si_20.6U_20.6 the largest amount of low energy modes is annealed out at lowest energy.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday     

Fluctuations in inelastic proton scattering from58Ni in the energy range 17.1 to 20.6 MeV

Excitation functions of proton elastic and inelastic scattering on⁵⁸Ni have been measured for proton energies in the range 17.1 to 20.6 MeV, at laboratory angles of 90°, 120° and 155°. All show cross section fluctuations. Excitation functions are presented for the elastic and for five inelastic groups in the energy range 18.1 to 18.59 MeV. These were analyzed by the Fourier analysis method, and the average level width found to be about 13 keV. The observation of strong fluctuations in the higher inelastic yields has implications for several microscopic analyses reported in the literature of⁵⁸Ni(p, p′) data obtained at 17.7 MeV incident proton energy.     

Electrical transport and thermal properties of ferromagnetic shape memory alloy Ni49.4Mn30Ga20.6

The electrical transport and thermal properties of the ferromagnetic shape memory alloy Ni_49.4Mn₃₀Ga_20.6 are measured. Near around the starting point from austenite to martensite transition, the temperature (T) dependence of resistance for the sample shows a clear jump due to a great scattering mechanism introduced by the transformation resulting in many interfaces during the process. T-dependent curve of the thermoelectric power (S) of the sample shows linear dependence below martensitic transformation temperature with its absolute value decreasing during cooling. The absolute value of S   tends to reach at a maximum at the martensitic transformation which is reflected by ∂S/∂T$\mathrm{\partial }S/\mathrm{\partial }\mathrm{T}$∼0. This may be related to the changes of the density of states near the phase transformation and the corresponding scattering introduced.