Kazuo Miyatani

Magnetic Susceptibility and NMR Studies of XAI-Type Intermetallic Compounds (X=Ni, Co and Fe)

Magnetic susceptibility and nuclear magnetic resonance of Al 27 and Co 59 were studied for Ni-Al, Co-Al, and Fe-Al intermetallic compounds with CsCl-type structure. Curie-Weiss type paramagnetism was observed for the Fe-Al and cobalt rich Co-Al compounds, and Pauli type paramagnetism was observed for the Al rich Co-Al and all Ni-Al compounds. A temperature independent negative Knight shift of Al 27 was observed in the Fe-Al system. The line width increases in the Fe-Al and Co-Al compounds when Al content decreases and Curie-Weiss type paramagnetism appears. The line intensity shows a sharp maximum at the stoichiometric composition XAl, and decreases steeply to the both sides due to the effects of quadrupole interactions. All the results have been discussed based on the band model. It is concluded that the excess Co and Fe atoms make small clusters to which the positive increase in the susceptibility and the line broadening are attributed, and that the vacancies at the Ni and Co sites in the Al-rich sides ...

Magnetic Properties of Single Crystal Chalcogenide Spinels; CuCr2X3Y (X=S, Se and Te, Y=C1, Br and I) System

The new compounds CuCr 2 S 3 I and CuCr 2 Te 3 Br have been prepared in powder form. Single crystals of CuCr 2 S 3 Cl, CuCr 2 S 3 Br, CuCr 2 Se 3 Cl, CuCr 2 Se 3 Br, and CuCr 2 Te 3 I have been also grown. The magnetic properties of these compounds have been studied. Among these compounds, only the magnetic moment of CuCr 2 Se 3 Br (5.54 µ B /mole) is higher than that of CuCr 2 X 4 system (5 µ B /mole). The magnetic moment of CuCr 2 Se 3 Cl and CuCr 2 Te 3 I is very close to 5 µ B /mole, while the sulfides CuCr 2 S 3 Y exhibit more complicated magnetic properties. The electrical resistivity of the single crystal CuCr 2 Se 3 Br shows a semiconductive behavior.

Magnetic and Electrical Properties of Impurity Doped HgCr2Se4

Measurements of the magnetic properties and the electrical properties (the electrical resistivity, the Hall effect and the magnetoresistance effect) were performed on hot pressed polycrystalline samples of Hg 1- x Ag x Cr 2 Se 4 (0≤ x ≤0.0155) and of Hg 1- y In y Cr 2 Se 4 (0≤ y ≤0.02). It was found that the Curie temperature of Hg 1- x Ag x Cr 2 Se 4 increased as the amount of the Ag dopant increased, whereas the Curie temperature of Hg 1- y In y Cr 2 Se 4 decreased with increasing concentration of the In dopant. The In-doped HgCr 2 Se 4 showed a high resistivity, a large Hall effect, and a large negative magnetoresistance effect; the Ag-doped HgCr 2 Se 4 showed a low resistivity, a small Hall effect and a small critical scattering of positive magnetoresistance. The different effects of the dopants. Ag and In, on the properties of HgCr 2 Se 4 which were studied is satisfactorily explained by the change in carrier concentration produced by the dopants.

Cylindrical parabolic solar mirrors

A solar cylindrical parabolic mirror with a 730 x 2600 mm aperture and a 105 mm focal length has been designed and built by elastically bending thin glass mirror sheets. This parabolic mirror was used to build a precission solar concentrator with a high collection efficiency for incident light. (AIP)