Motoyuki Nomura

Measurement of the Resistance of Manganin under Liquid Pressure to 100 kbar and Its Application to the Measurement of the Transition Pressures of Bi and Sn

The electrical resistance of manganin wire and the X-ray diffraction of NaCl were measured simultaneously under hydrostatic pressures up to 100 kbar using a cubic-anvil type pressure apparatus at room temperature. The solidification pressures of 1: 1 pentane-isopentane and isopropanol were determined by taking advantage of the sensitivities of the resistance of manganin wire to the local stress. The transition pressures for BiIII↔V and SnI↔II were measured in both loading and unloading by detecting the pressure where the high-pressure phase and the low-pressure phase coexist.

Anisotropic Lattice Compression in Fe2P

Lattice compressions along the a - and c -axes of compounds Fe 2 P and Ni 2 P were measured at room temperature by means of X-ray diffraction under hydrostatic pressures up to 100 kbar. Compressions were linear with pressure, and the a -axis was more compressive than the c -axis in Fe 2 P, while the situation was reverse in Ni 2 P.

Theoretical Study of Hysteresis Phenomena of Pressure-Induced Polymorphic Transition in Alkali Halides

The lattice energy was calculated on the way of the transition of KCI by the use of the transition mechanism proposed by Watanabe et at ., and it was found that the potential barrier appeared between two phases, the B1 and the B2 structures. Due to the existence of the potential barrier, it was indicated that the hysteresis phenomena were derived in the pressure-induced polymorphic transition, and that the width of the hysteresis could be obtained quantitatively. The temperature dependence of the hysteresis also can be explained by the concept that the barrier can be got over by the thermal energy.

A Pressure Cell for the Measurement of the Curie Temperature with the Cubic-Anvil Press

A pressure cell was developed for the measurement of Curie temperature, Tc, under pressure with the cubic-anvil type pressure apparatus. Using the new cell, a nonlinear behavior similar to that observed by Leger et al. was observed in the pressure dependence of Tc of Ni. The pressure derivatives of Tc at low pressure of disordered Ni–Mn alloys up to 23.2 at.% Mn were measured with the new cell and the standard press bomb connected to a pressure intensifier.

Orientation Relation in the Pressure-Induced Transition B1→B2 of RbCl Observed by an X-Ray Four-Circle Diffractometer

The orientation distribution of the {110} diffracted line of the pressure-induced B2 phase of RbCl after Bl→B2 transition was measured with an X-ray four-circle diffractometer on which the Merrill-Bassett type diamond anvil pressure cell was mounted. Judging from the {110} pole figure of the B2 phase, the center of which is the [100] axis of the B1 phase, the orientation relation was [111](B2)//[100](B1) and [100](B2)//[111](B1). The result agreed with that obtained by Okai from X-ray diffraction photography.

The Measurement of the Resistance of Manganin Wire with the Cubic-Anvil Type Pressure Apparatus

A pressure cell was developed for the simultaneous measurement of the X-ray diffraction of an internal pressure standard and the electrical resistance of Manganin under the hydrostatic pressure generated by a cubic-anvil type press. Using this pressure cell, the Manganin resistance was measured under pressure calibrated by an internal pressure standard, NaCl, over a continuous pressure range up to about 40 kbar. A linear relationship between the resistance and the pressure was observed over the entire pressure range, and the pressure coefficient of the resistance was 0.23%/kbar. The effect of the nonhydrostaticness of pressure if discussed.

Effect of Hydrostatic Pressure on the Magnetocrystalline Anisotropy Constant K1 of Ni-Pd Alloys

The effects of hydrostatic pressure on the first magnetocrystalline anisotropy constant K 1 were measured on both Ni–Pd (∼40 at.%Pd) and Ni–Cu(∼19 at.%Cu) alloy systems in Ni rich regions by torque method. Measurements were made under pressures up to 6 k bar at 77 K for both Ni–Pd and –Cu alloys and at 273 K for Ni–Pd alloys. The pressure derivatives of K 1 , ∂ K 1 /∂ P , are all positive in sign for both alloy systems. At 77 K, ∂ K 1 /∂ P increases rather slowly with Pd content for Ni–Pd alloys, but it decreases rapidly with Cu for Ni–Cu alloys. The positive shift of K 1 with pressure and the different behaviour of ∂ K 1 /∂ P at 77 K for both alloy systems are discussed qualitatively on the itinerant electron model.

Pressure Effects on the Curie Temperature of (Co1-xMnx)2P

Measurement of the Curie temperature was made on the (Co 1- x Mn x ) 2 P, 0.3≦ x ≦0.7, compounds by the ac susceptibility under pressure up to 60 kbar. The Curie temperature T c of each concentration increased with increasing pressure and was represented by a function of pressure, P , as T c = T c 0 +α P +β P 2 . The constants T c 0 ( T c at P =0), α and β took maxima in the vicinity of x =0.5. The results obtained are analyzed on the basis of the pair interaction model, and it was suggested that the interatomic-distance dependence of the exchange interaction energy between the Mn atoms oscillates.

Measurement of the Resistance of Manganin Wire with Cubic-Anvil Type Pressure Apparatus. II

The electrical resistance of manganin wire was measured together with the X-ray diffraction of the pressure marker under hydrostatic pressures up to 60 kbar with a cubic-anvil type pressure apparatus. A time-dependent change in the resistance was observed after all the valves of the hydraulic press had been closed, and it was confirmed that this resistance change was due to a change in the pressure itself within the sample chamber. The resistance increased with pressure in an approximately linear manner. The solidification pressure, Ps, was estimated for isopropanol from the resistance anomaly observed and it was found to be lower by several kilobars than so far reported. Hysteresis in the resistance-pressure curve was also observed above Ps, and this was attributed to the pressure distribution within the sample chamber.

Determination of the Transition Pressures of Some Alkali Halides under Hydrostatic Pressure with X-Ray Diffraction Method

Although many reports have been presented concerning the polymorphic transition pressures of alkali halides, there have been few reliable studies with respect to the hysteresis phenomena. Recently Lacam and Peyronneau [1] observed the definite hysteresis loops of several rubidium halides Controlling such conditions as purity of the specimen, heat treatment, and pressurization rates. For the potassium halides, on the other hand, which have higher transition pressures [2] than those of rubidium halides, no reliable hysteresis loop was reported. Mizouchi [3] measured the transition pressures of potassium chloride as a test of his new pressure apparatus both in compression and decompression runs, but his result is unlikely to be regarded as a hysteresis loop. In order to explain the hysteresis phenomena, therefore, the lattice constants of the potassium halides were measured using the x-ray diffraction technique at pressures including the phase transition. The specimens studied were KCl, KI, KBr, and KF.