Nobuo Mōri

Pressure effects on Tc of superconductor YBa2Cu4O8

The enhancement of the superconducting transition temperature by pressure was studied up to 2 GPa for an YBa2Cu4O8 compound which was synthesized by using the canned HIP technique. The value of dTc/dP was found to be 5.5 K/GPa. From the experiments of the specimen in which YBa2Cu4O8 and Y2Ba4Cu7O14 compounds coexist, dTc/dP for Y2Ba4Cu7O14 was also shown to be 5.5 K/GPa. The result for the YBa2Cu4O8 compound is explained by the pressure induced carrier (hole) redistribution on the basis of the calculation of the Madelung energy.

Valence instability of the heavy fermion compound CeCu6 under high pressure

Abstract The electrical resistivity ρ of the heavy fermion compound CeCu6 has been measured under high pressure up to 8 GPa in the temperature range 4.2

Pressure dependence of the crystal field state of a low carrier system CeP

Abstract Pressure dependence of the crystal field splitting in CeP has been studied by inelastic neutron scattering up to 0.8 GPa. It was found that the Γ7−Γ8 crystal field splitting in CeP decreases by about 10% from that at ambient pressure by applying a pressure of 0.8 GPa at temperatures below 60 K. Evidence for the temperature dependence of the pressure effect is seen.

Neutron scattering investigations of magnetic ordering and crystal field excitations in CeAs under high pressure

Abstract Elastic neutron scattering experiments on CeAs have been performed under high pressure. A new magnetic ordering with a ferromagnetic component is induced above ∼1.1 GPa, and a magnetic P-T phase diagram up to 3 GPa is determined. A qualitative aspect for the relation between the pressure-induced new magnetic phase and the crystal field splitting is discussed.

The effect of pressure on the Néel temperature of URu2Si2

Abstract The temperature dependence of the electrical resistivity of the intermetallic compound URU 2 Si 2 was measured up to 80 kbar in order to examine the stability of the antiferromagnetic state at high pressures. It was found that the Neel temperature T N (approximately 17 K at 1 bar) increases with increasing pressure at a rate of about 0.2 K kbar −1 below 20 kbar. The increase in T N becomes very sluggish at high pressures (above 50 kbar), with a broad maximum around 80 kbar.

Effect of pressure on the electrical resistivity of URu2Si2

Abstract The electrical resistivity ρ ( T ) of the concentrated Kondo compound URu 2 Si 2 has been measured at high pressure up to 80 kbar in order to examine the stability of the electronic state at high pressure. The pressure dependence of volume is also observed by X-ray diffraction. The Gruneisen parameters for the Neel temperature and the Kondo temperature are estimated on the basis of the results in the present work. The present analysis emphasizes the itinerant character of 5f electrons of URu 2 Si 2 .

Pressure Effect of the Lattice Parameters for Mn2Sb and MnMGe (M=Al, Ga)

High-pressure powder X-ray diffraction experiments have been performed for Mn2Sb, MnAlGe and MnGaGe up to a pressure of 7.7 GPa at 300 K. Mn2Sb exhibits a discontinuous change in the lattice parameters a and c at about 3.5 GPa with increasing pressure. For MnAlGe and MnGaGe, the lattice parameters decrease linearly with increasing pressure.

Effect of pressure on the electrical resistivity of CePtSi2

Abstract Electrical resistivity ϱ( T ) of the concentrated Kondo compound CePtSi 2 has been measured as a function of temperature at various pressures up to 80 kbar. Two maxima are observed near 5 K (= T 1 ) and 28 K (= T 2 ) in the ϱ( T ) curve at ambient pressure. It is found that T 2 increases with increasing pressure but T 1 , disappears above 5 kbar and the two maxima are merged into a broad maximum above 20 kbar. The overall behavior of the ϱ( T ) curves at high pressures indicates that a crossover in the electronic state of CePtSi 2 is induced by applying pressure. On the basis of the data in the present work, we examine a semi-quantitative analysis to obtain the value of | JN (0)| at ambient pressure.

High-Pressure X-Ray Study on (L1-xAx)aCubOcSystem

The (L1-xAx)aCubOc system have high Tc superconductivity, where L stands for La, Y and so on, A for the alkaline earth elements, like Ba, Sr and so on. The pressure effect on the lattice constants of YBa2Cu3O7-y has been measured at room temperature up to 60 kbar. Compression coefficients of a- and c-axis are found to be almost the same value of (3.3±0.3)×10-4 kbar-1, which is larger than the value for (La0.9Sr0.1)2CuO4 and the ratio of c/a is found to be almost constant, whose tendency was observed in (La0.9Sr0.1)2CuO4. But the ratio of a/b decreases slightly under pressure.

Dielectric dispersion in BaTiO3 single crystal at low temperatures

Abstract The dielectric constants of BaTiO3 single crystals grown by a flux method and a top seeded solution growth (TSSG) method have been reexamined in a wide temperature range of 15K–450 K and in a frequency range of 30 Hz–1 MHz. A low frequency dielectric dispersion with an intensity of Δ έ ≈1500 appears at around 100 K only on the crystals grown by the TSSG method. Results of an electric field cooling treatment on the (100) c or (111) c plates indicate that the dispersion is not due to usual domain-wall motions.