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An atomic-scale graded structure has been formed previously in a Bi70Sb30 (at. %) alloy that is miscible in all proportions, by sedimentation of substitutional solute atoms under an ultrastrong gravitational field up to 1×106 G at 220–240 °C [T. Mashimo, T. Ikeda, and I. Minato, J. Appl. Phys. 90, 741 (2001)]. In this study, additional megagravity field experiments were performed on the Bi70Sb30 alloy and pure Bi at different temperatures below their melting points, to investigate the change in crystalline state under the ultrastrong gravitational field. For the Bi70Sb30 alloy ultracentrifuged at 191–205 °C, no change in composition was observed, and the grain sizes of the crystals decreased from several millimeters to tens of micrometers, while no distinct change in grain size was observed for the pure Bi ultracentrifuged under the same experimental conditions. The Bi70Sb30 alloy ultracentrifuged at 220–240 °C consisted of two regions with different morphologies–fine-grained crystals with grain sizes in ...

An ultracentrifuge apparatus, which can generate an ultra-strong gravitational field even >1 000 000 (1 million) G (1 G=9.8 m/s2) over a wide temperature range up to >500 °C with high stability control, was developed for new materials science research. The system consists of an air turbine motor with ceramic ball bearings and dumper section, a sample rotor with an outer diameter of up to 160 mm, a vacuum chamber, and a heating system. The nonbored rotor and the double-structural dumper bushing are used to raise the maximum rotational speed and to improve the stability. The samples can be heated by radiant heat. A maximum rotational speed of 190 000 rpm using a 70 mm diam rotor was recorded despite a short time where the maximum gravitational field was >1 2000 000 G. Long and high-temperature ultracentrifuge experiments using 70 and 80 mm diam rotors made of titanium alloy with rotational speeds of up to 170 000 rpm even at temperatures of over 200 °C for 100 h with ripples of

Electrical resistivity measurements have been made on a good qualified single crystalline magnetite (Fe3O4) at temperatures from 300 down to 3.0 K under pressure up to 10 GPa. A steep change in resistivity at the Verwey transition temperature has been observed at pressure below 6.5 GPa, which shows a quite distinct result reported in prior work. Moreover, the Verwey transition temperature has been found to decrease nonlinearly with increasing pressure and it disappears at around 8 GPa. Above 8 GPa magnetite exhibits metallic behavior. The residual-resistivity ratio of the metallic state is observed to be more than 350. This finding of a metallic ground state in magnetite provides insight into the understanding of the Verwey transition in magnetite.

The approximate d bands of antiferromagnetic α‐Mn are formulated, using Deegan’s prescription and the formulas of Slater and Koster, in consideration of the crystal and magnetic structures. The magnetic moments of 29 atoms are calculated by adopting reasonable coefficients of the effective exchange interaction. The obtained result is much the same as the experimental result.

The approximate d bands for YCo5, RCo5, Y2Co17, and R2Co17 (Th2Zn17 and Th2Ni17 type) are formulated by Deegan’s prescription and the formulas of Slater and Koster. The experimental results of YCo5 and Y2Co17 are discussed by using these approximate d bands. For RCo5 and R2Co17 the discussions are made by adopting the localized model and the band model for 4f electrons.

The approximate d bands for the ordered Ni3Al crystal are formulated by Deegan’s prescription and Slater and Koster’s formulas in the tight binding approximation. The electronic energies of this crystal with the spin direction parallel to [100] and 110] directions are calculated by using Gilat and Raubenheimer’s method. Then, the anisotropy constant K1 is estimated, which is in agreement with the experimental result. The temperature dependence of K1 is also discussed. It is found that the temperature variation of the Fermi level for these two states is appreciably different with each other by analyzing the experimental result, and this can be explained by the d‐band structure of this crystal.

The d bands for RCo5, R2Co1 7, and R6Mn2 3 compounds are formulated by Deegan’s prescription and the formulas of Slater and Koster. The d‐f elements for these energy bands derived by Lendi are taken into account. The spin polarization of the f bands are investigated. The obtained result explains the experimental result by taking into account the feeble exchange splitting in 4f bands. Additionally, the magnetic moment of rare earths is calculated on the basis of the band model and the calculated result is compared with g J. It is found that in these compounds the spin polarization is saturated and the moments are much the same as g J.