Tadayasu Mitsui

Localized Magnetic Moments and Pauling Valence in Manganese Metal, Some 3d-Transition Alloys and Intermetallic Compounds

The dependence of magnetic moments localized at manganese atomic site on crystalline environment is discussed by using the concept of the Pauling valence which is defined by the relation between the atomic radius and the interatomic distance from neighbouring atoms. The linearlity of the magnitude of magnetic moments and the Pauling valence at individual manganese atomic site is found. It is concluded that the localized magnetic moment is mainly affected by kinds of nearest neighbour atoms and the coordination number. From this result, it is suggested that the covalency effect plays an important role in determining the magnitude of the magnetic moment assosiated with the manganese atomic site. Magnetic moments in σ-phase Fe-V alloys whose crystal structure is similar to that of α-Mn are also discussed.

A New Allotropic Phase of Cerium above 121 kbar

It is well known that cerium metal appears in many different allotropic phases. The existence of two fcc phases, γ and α, has been the subject of extensive study particularly relative to the behavior of the 4f electrons in this transition. At pressures higher than 50 kbar, α-Ce transforms to a superconducting α′ phase [1]. Conflicting results have been reported on the crystal structure of α′-Ce [2–6]. During the course of an x-ray diffraction study to clarify this Situation, we found another allotropic phase around 120 kbar pressure. This paper deals with the crystal structure of the new phase and the resistance change associated with the transition from the α′ phase to the new phase.

Magnetic Properties of σ-Phase of Some 3d-Transition Alloys

Magnetic susceptibility measurement has been made on the σ-phase of Fe-V, Co-V, Ni-V and Co-Cr binary alloys. The Fe-V system only is ferromagnetic. The temperature dependent parts of the susceptibility of Fe-V alloys obey the Curie-Weiss law. The paramagnetic moment µ per iron atom in Fe-V varies with vanadium concentration C v following an empirical relationship, µ/µ B =-2.62+173/ C v , where C v is atomic-% of vanadium. The Curie temperature is sensitive to heat treatments of the specimens, but the magnetic moment is not affected. The susceptibility of the other alloys is found to be nearly temperature independent. The magnitude of the magnetic moment localized on magnetic atoms at different kinds of sites in these σ-phase is suggested.

The Critical Exponent of the Anisotropic Electrical Resistivity in the Vicinity of the Neel Temperature of Chromium

Anisotropic resistances with respect to the spin-density-wave vector Q of a single-crystalline chromium were measured near T N . Their temperature derivatives are analyzed by a power law. In the equation of dρ/d T =- A e -λ + B , where A and B are both positive constant, the index λ is about 0.5 for T T N . The indexes are almost isotropic with respect to Q . For T < T N , it is considered that the value of λ originates from the order parameter, that is, the temperature dependence of the SDW energy gaps. The index of the order parameter β is estimated to be 1/2 which agrees with its classical value. The additional date obtained in the multi- Q state are also discussed.

Effect of Magnetic-Field Cooling through the Anomaly Temperature in Vanadium Metal

The effect of magnetic-field cooling was measured on a single crystal of vanadium metal of 99.9% purity using a sensitive torque-magnetometer. It was found that uniaxial anisotropy with the easy axis parallel to the cooling field was induced by the magnetic-field cooling from 300°K down through the anomaly temperature to 87°K with cooling field 13 kOe, and that the induced anisotropy disappeared precipitously when the specimen was heated up to 280°K, which is ascribed to the anomaly temperature of this specimen. It is suggested that the anisotropy is due to the preferably oriented phase of vanadium hydride which has small spontaneous magnetization.

A Simple X-Ray Camera for High Pressure Uses

An extremely simple camera has been developed which enables X-ray powder diffraction under pressures up to 100 kbar at room temperature. A thick cylinder of a pressure vessel acts as a body of a Debye-Scherrer camera. A pressure-clamping method is used. To test the camera, the lattice parameter of NaCl has been measured at the Bi III-V transition point.

Magnetic Field Dependence of the Hall Coefficient in Low Temperature on the Antiferromagnetic Chromium

The Hall coefficient, R H , of single crystal and single Q state of pure Cr was measured in magnetic field up to 45 kG at 4.2 K and in higher temperature. In each measurement, anomalous behaviors on R H were found at about 2 and 10 kG, and reversal of the sign of R H from positive to negative was observed below 45 kG at 4.2 K. Remarkable changes of 2 and 10 kG were also found on R H against temperature and these were discussed through magnetic breakdown with the gaps on spin density weve state of Cr.

X-Ray Measurement on the Compression of NaCl to 80 kbar at Liquid Nitrogen Temperature

An X-ray camera for use at high pressure and low temperature was designed to measure the lattice parameter of NaCl as a function of pressure up to 80 kbar at liquid nitrogen temperature. The change in pressure on cooling the clamp vessel was corrected by using the lattice parameter-pressure relation of Si at room temperature. The result on the pressure-volume relation of NaCl is in agreement within the experimental error with simply extended Deckers calculation of the equation of state of NaCl.

Pressure Effect on T2-Dependence in Electrical Resistivity of α-Ce and α-Ce0.97La0.03 Alloy

The electrical resistivity of α–Ce and α–Ce 0.97 La 0.03 alloy was measured as a function of temperature in the range of hydrostatic pressure from 0 to 10 kbar. The values of the coefficients ( A ) of T 2 -term decreased with increasing pressure and increased with a concentration of La. The value of A at 3 kbar obtained in the present work was about half of the one by Katzman and Mydosh.

The temperature dependence of the resistance and the spin density wave energy gap of antiferromagnetic chromium

Abstract The anisotropic electrical resistance of antiferromagnetic chromium was measured in the temperature range of 10 K – 200 K. The two-band model was used to analyze the temperature dependence of the resistance, considering the effective number of conduction electrons associated with the SDW energy gap.