Yasushige Fukano

Magnetic properties and the electronic structure of a stable Al-Cu-Fe icosahedral phase

The stable Al-Cu-Fe icosahedral phase showed almost no local magnetic moment at low temperatures, and a dependence of the magnetic susceptibility linear to the square of the temperature above about 150 K. The former is interpreted by the condition of the local magnetic moment formation according to the theory of Friedel and Anderson, and the latter affords strong experimental evidence for the band gap corresponding to the Brillouin zone inferred for strong diffraction spots. An experimental value of the mass density is obtained, in order to estimate the electron number density.

Crystal Structure and Morphology of Fine Particles of Vanadium Silicides

In this experiment, fine particles of various vanadium silicides were made by the gas-evaporation technique. The structure and morphology of the particles were observed by electron microscope. The A15 structure was found to appear at 20.0 and 25.0 at.%Si, while the D88 and D8m structures appeared at 35.2 and 37.5 at.%Si. The particles were surrounded by crystallographic planes with low Millers indices characteristic of each structure. At 30.0 and 32.7 at.%Si, two types of particle were observed; one containing the A15 and D8m structures and the other the A15 and D88 structures. In the respective particles, the lattice relationships (001)A15//(001)D8m and [100]A15//[100]D8m , and (001)A15//(001)D88 and [110]A15//[120]D88 , were found. These can be ascribed to the resemblance between the structures.

High-temperature magnetic properties of a stable Al65Cu20Fe15 icosahedral phase

The field and temperature dependence of the magnetisation is studied in a stable Al-Cu-Fe icosahedral phase, in the temperature region between 77 and 1050 K and in magnetic fields up to 18 kOe. The sample shows a good quality of structural perfection in X-ray diffraction and electron microscope observations as compared with known icosahedral phases. The magnetic susceptibility shows an increase from -1.5*10-7 to 4.5*10-7 EMU g-1 with a rise in temperature from 150 to 1050 K, which has not been observed icosahedral phases studied to date.

Planar Defect in A15 Structure Observed in Cr-Si Fine Particles

A new planar defect in the A15 structure was found in fine particles formed by the evaporation of Cr–Si alloy in Xe gas. Electron microscopic analysis showed that the planar defect lies on the {100} plane and the displacement vector due to the defect is a. A probable model of the defect is proposed.

Crystal Structure and External Shape of Fine Particles of Beryllium Produced by Evaporation in Inert Gases at Low Pressures

It has been found by electron microscopy and electron diffraction that fine particles with the monoclinic lattice are formed in beryllium smoke produced by the evaporation of beryllium metal in inert gases at low pressures. The lattice constants are determined as a=5.49, b=6.10, c=4.10 A and β=98.5° within an error of 0.2%, the space group is either Cs4 or C2h6, and the external shape of the particles is very like a rhombic dodecahedron. This monoclinic beryllium is a new allotrope of beryllium. Rhombic dodecahedral particles of α-beryllium are also found, produced from the monoclinic particles by martensitic transformation.

Superconducting Transition Temperature of Fine A-15 V-Si Alloy Particles

The superconducting transition temperature ( T c ) of the fine particles of V–Si alloys with A-15 structure is studied. The average diameters range from 40 to 8000 A. The T c of the particles with the stoichiometric composition smaller than 170 A is about 6∼7 K, which is less than half of that of the bulk material. The T c of the particles with 22.0 and 20.0 at%Si is below 2.0 K, and increases to about 3 K after the annealing at 780°C for 4 hours. The large reduction in T c is interpreted in terms of the broadening of the peak in the electronic density of states caused by the break-down of the translational symmetry in the particles.

V51 Knight Shift in Fine V3Si Particles

The Knight shift of vanadium (KV) in fine V3Si particles was studied. The average diameter () ranged from 60 to 8000 A. The strong temperature dependence of the KV characteristic of high-Tc A-15 compounds was weakened in the particles. KV at 77 K increased with a decrease in . The above-mentioned trends were consistent with a broadening of the sharp peak in the electronic density of states around the Fermi energy in particles resulting from a perturbation of the surface.