Post-collision interaction is investigated on the spectra of Ar L₃M₂₃M₂₃ Auger electrons which are created by electron impact of energies from 257 eV up to 2000 eV. The spectral shape has been analyzed by taking into account the finiteness of the velocities of both the receding and Auger electrons. Disappearance of the post-collision interaction is found at the highest electron-impact energies.

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The nuclear magnetic relaxation rate, 1⁄T₁, of ¹⁹⁵Pt in a normal and superconducting state was measured. In the normal state, 1⁄T₁ is proportional to T, indicating the Fermi liquid nature of the system. In the superconducting state, 1⁄T₁ has no enhancement just below the transition temperature and varies in proportion to T³ at low temperatures. These results indicate the existence of an anisotropic superconducting energy gap, which vanishes at lines on the Fermi surface.

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A group-theoretic argument is given to obtain possible forms of a pairing interaction which is short-ranged in nature and to enumerate pairing wave functions allowed under a certain crystalline symmetry, e.g., a two-dimensional square lattice. The implications of the results are discussed in conjunction with high-T_C oxide superconductors and heavy Fermion materials.

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The mean field critical temperature, T_c, of superconductivity in the presence of a superexchange interaction has been calculated by taking the resonating valence bond (RVB) amplitude and the boson kinetic energy self-consistently as a function of the transfer integral, t, the superexchange interaction, J, and the concentration of the vacant site, δ. For δ\lesssimJ⁄t, the Bose condensation of slave bosons sets the critical temperature, although for δ\gtrsimJ⁄t, the onset of the RVB pairing corresponds to that of superconductivity. It is found that T_c has a maximum around δ\backsimeqJ⁄t.

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A field-induced metamagnetic transition has been observed in the valence fluctuating intermetallic compound Yb_xIn_1−xCu₂ (0.25≤x≤0.55) around 300 kOe at 4.2K. The temperature dependence of the susceptibility for the samples with 0.25≤x≤0.6 has also been measured. It is shown that the metamagnetic transition is correlated closely with the Yb-valence transition observed at about 40 K in the susceptibility measurement.

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The nuclear spin-lattice relaxation time T₁ of ⁶⁹Ga and ⁷¹Ga in the antiferromagnetic Heusler alloy Ir₂MnGa has been measured in the paramagnetic state. The observed 1⁄T₁ for T>>T_N is explained quantitatively by the exchange-coupled localized moment fluctuations. This indicates that the correlation time of the paramagnetic spin fluctuations is well characterized by the exchange frequency of localized moments, in contrast to the case of the temperature-induced localized moments where the frequency spectrum of the fluctuations spreads over a much higher frequency.

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Complex dielectric constants of PbHPO₄ and PbDPO₄ have been studied at frequencies from 10³ Hz to 10⁹ Hz in the Curie temperature region. The Curie-Weiss behavior of the low-frequency dielectric constant is confirmed. The dielectric dispersion of the Debye type which shows a critical slowing-down has been observed in both materials. The phase transition is considered to be of an order-disorder type. The effects of deuteration in the static and dynamic dielectric properties are discussed.

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Explicit solutions of a model equation describing the motion of melts in the Earth are obtained by an independent variable transformation. Included are periodic wave solutions, solitary wave solutions and weak solutions with compact support. It is also discussed that if the model equation is modified, the resultant equation can be reduced to the exactly solvable Korteweg-de Vries equation.

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The inverse scattering of the M×M-order eigenvalue problem is developed systematically by virture of Riemann-Hilbert problem. The Gel’fand-Levitan equation is obtained, under certain restriction on the discrete scattering data, according to the new derivation of kernel (integral) representations of the Jost functions on the spectral plane.

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A system of 2-wave interaction
(∂⁄∂t+c₁∂⁄∂x)u=−uv, (∂⁄∂t+c₂∂⁄∂x)v=uv,
is extended to a system of 2N-wave interaction
(∂⁄∂t+c₁∂⁄∂x)u_n=u_n(v_n−1−v_n),
(∂⁄∂t+c₂∂⁄∂x)v_n=v_n(u_n−u_n+1),
for n=1, 2, 3…, N with the boundary condition v₀=u_N+1=0, where c₁ and c₂ are the velocities of the waves. Exact solutions including 2N arbitrary functions are obtained.

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Relationship between Husimi function ρ_H and distribution function ρ_CC in coarse-grained classical mechanics is studied where ρ_CC is introduced by same manner of coarse-graining in Husimi function. Defining the product of dynamical variables and Poisson brackets in coarse-grained classical mechanics, we reduce the equations for time development of the quantities. Particularly, ρ_CC shows good correspondence to ρ_H in early stage of time development, but shows poor conformity after quantum interference appeared.

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A generalized version of the terrace-step-kink (TSK) model is introduced to study in detail the shape of a crystal near the facet edge. The model is analyzed by the transfer-matrix method combined with the lattice fermion approach. As a result, behavior of the curvature near the facet edge is found to have unexpected new features: finite Gaussian curvature jump with universal amplitude and vanishing transverse curvature with universal exponent.

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Magnetohydrodynamic stability of an infinite self-gravitating, inviscid and perfectly conducting medium with streams of variable velocity distribution is investigated for general wave propagation. The streaming motion has a destabilizing influence on the medium. The magnetic field exerts a strong stabilizing effect which causes the bending of the magnetic force lines. The medium is unstable only for certain values of the wave number and stable for all other values. The instability Jean’s criterion of a static medium is unaffected by the inclusion of the magnetic field effects, even if it is with a uniform streaming.

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The transverse plane waves propagating in the horizontal direction in an unbounded binary fluid mixture having vertical temperature and concentration gradients are investigated. It is shown that the conditions found by Bhattacharyya and Gupta (Phys. Fluids 28 (1985) 3215) for the propagations of undamped waves or weakly damped waves in the low-frequency limit contradict the stability criteria for the undisturbed basic state. It is also shown that weakly damped waves can exist under the conditions that the undisturbed basic state is stable.

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In the present paper a Korteweg-de Vries equation with a sinusoidal force and a small coefficient of dispersion is considered, and by means of numerical computations it is shown that a class of periodic stationary solutions, found in a previous paper and interpreted as describing a balance between the nonlinearity and the external force, is neutrally stable.

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The Marangoni instability due to a chemical absorption is studied theoretically by taking into account the mass transfer of gas, solute and product resulting from an irreversible reaction. It is found that the critical Marangoni number for the inactive product and the corresponding critical wavenumber change in a complicated manner depending on various parameters involved. Furthermore, it is found that the active solute leads also to the Marangoni instability, where roles of the gas are discussed as well. The Marangoni effect due to the product and that due to the solute are coupled so as to reinforce each other. Effects of the surface deformation give rise to another type of instability in the limit of zero wavenumber.

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Linear stability theory is applied to the problem of the onset of surface-tension-driven instability in a horizontal layer of binary liquid mixture confined at the bottom by a rigid, thermally insulating wall and at the top by a non-deformable free surface at which Newton’s cooling law is assumed to hold. It is also assumed that the liquid layer is heated by uniformly distributed internal heat sources which produce a nonlinear temperature profile and, in addition, a nonlinear concentration profile through the Soret effect. By neglecting small terms including the Soret coefficient S_T, an eigenvalue system of eighth order is derived and is then solved exactly. For wide ranges of various parameters, the conditions under which instability sets in are determined numerically. As compared with the corresponding linear temperature case (M. Takashima: J. Phys. Soc. Jpn. 47 (1979) 1321; 49 (1980) 802), it is found that the nonlinear temperature profile produced by internal heat sources makes the liquid layer less stable for both stationary and oscillatory modes.

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A theoretical model of the existence of ion acoustic double layers in a plasma with electron drift velocity less than the electron thermal speed which has already been observed experimentally and in numerical simulation, has been presented in this paper. The velocity and thickness of these double layers have been calculated.

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Plasma potential formation in an open-ended plasma confinement system with RF plugging (the RFC–XX–M device) is investigated. The plasma potential in the central confinement region is measured with a heavy ion beam probe system and potentials at the RF plug section are measured with multi-grid energy analyzers. The measured plasma potential is compared with that deduced from the generalized Pastukhov formula. Results show that the plasma potential develops as an ambipolar potential to equate ion and electron end losses. During RF plugging, electrons are heated by Landau damping, while ions are not heated since adiabatic conditions are satisfied during ion plugging in this experiment.

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Nonlinear coupled equations describing the low frequency interchange modes in a plasma with small fraction of the hot electron component are derived on the basis of multi-fluid equations. Stationary vortex solutions in a long wavelength limit are obtained in a plasma stabilized by the charge unconvering effect instead of the finite Larmor radius effect. The solution takes a form of a pair of localized vortices, rotating in opposite directions and moving with a constant velocity in direction perpendicular to the magnetic field. Linear dispersion relation is studied in detail. The dispersion relation of vortex, relating the propagation velocity to the core size of vortex is examined for typical parameters in bumpy torus experiments. Consequently, the positive and negative branches of the propagation velocity for the fixed size of vortex are also found.

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Excess diffraction lines observed as black lines across the 220 thermal diffuse spot and near the incident beam spot on X-ray film photographs of absorbing perfect germanium crystals were studied experimentally in detail by using monochromatized synchrotron radiations. The cause of the line was attributed to the anomalous transmission of the thermally scattered X-rays in the crystal. The experimental result was compared successfully with the theoretical calculation based on the dynamical diffraction theory of X-rays in the absorbing ideally perfect crystal.

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Defects in β-brass quenched from 973 K have been examined by the transmission electron microscopy. It is revealed that most of so-called black spot defects are voids of a rhombic dodecahedron surrounded by the {110} planes with the edges along the ⟨111⟩ directions. Almost all voids are connected to antiphase boundaries, suggesting that the ordering is promoted by the aid of quenched-in vacancies.

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Several liquid models considered to have a close connection with the network structure in B₂O₃ glass were proposed and the neutron and X-ray structure factors for the models were calculated by using the general procedure of analysis of structure factors for molecular liquids. From the agreement between the calculated values and the experimental data it was concluded that the structure of the glass was understood as that of the liquid composed of boroxol rings as ‘molecules’, where each boroxol ring is regarded as a rigid sphere in the hard sphere fluid: the effective hard sphere diameter is 4.18 Å and the packing fraction becomes 0.40. Intermediate range structure between two boroxol rings was also determined.

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Extended X-ray absorption fine structure (EXAFS) has been taken on the Se K-edge for isolated Se–Te mixed chains confined in the mordenite channels, as well as for trigonal and amorphous Se–Te mixtures. The Se–Se and Se–Te bond lengths in the Se–Te chain molecules have been determined by utilizing large difference in the wave vector dependence of backward scattering between Se and Te. The Se–Se and Se–Te bonds in the isolated chains are found to be shorter than those in the trigonal mixtures, which suggests that the intrachain covalent bonds are strengthened by reducing the interchain coupling. The Se–Se bond in the mixed chain molecule elongates with addition of Te, while the Se–Te bond changes little.

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Neutron diffraction measurement has been carried out in order to investigate the structure of molten silver iodide. The observed total structure factor and the pair distribution function of molten AgI have been compared with those of theoretical results based on the Hyper-Netted Chain model by Stafford and Silbert. Present experimental results agree well with the theoretical one and support the validity of their calculation.

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The crystal structure of β-CuI at 400°C has been refined from powder crystal X-ray diffraction data. The crystal belongs to the trigonal system with the space group C_3v¹-P3m1, and has lattice constants of a=4.279±0.002 A, c=7.168±0.007 A. The low temperature phase of solid electrolytes is often of tetrahedral structure such as zinc-blende or wurtzite. The structure of the β-CuI includes the ordered arrangement of Cu⁺ ions surrounded by tetrahedra of I⁻ ions.

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By using the method of geometrical inequalities, the ground state of the lattice gas model on the square lattice in which two kinds, A and B, particles interact by pairwise interactions extending to the second neighbors is determined rigorously for arbitrary values of the particle densities. The relation V_k^AA=V_k^BB=2V_k^AB is assumed for the kth (k=1, 2) neighbor interaction constants between the A and A (V_k^AA), B and B (V_k^BB), and A and B (V_k^AB) particles. It is found that various ordered structures of the A and B particles appear as the ground states. The ground state of the equivalent three-state Potts model on the square lattice with up to second neighbor interactions is also determined rigorously for arbitrary values of the interaction constants and the external fields.

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Two doubly periodic phases with ribboned shape are known to exist between monolayered smectic A phase and bilayered smectic A phase in certain binary mixtures. Phase transitions occurring successively among them are studied in an electric field on the basis of a model introduced recently by Benguigui.

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In order to investigate the interaction between a vacancy and 3d transition elements (Fe, Co and Ni) in Au, the annealing behaviour of quenched-in vacancies in dilute Au alloys is examined by means of precise electrical resistivity and positron lifetime measurements. Several sub-stages appeared in the recovery curve of both resistivity and positron lifetime, and they were explained by taking the motion of vacancy-solute pairs into account. From the analysis of the effective migration energies obtained in the final annealing stage where the dissociation of VS pairs were expected to take place, the binding energies of VS were obtained to be 0.35, 0.33 and 0.20 eV for Fe, Co and Ni solute, respectively. These values are fairly large, contrary to the theoretical calculations. Based on these results, the origin of the strong binding was pursued and the new concept of ‘covalency effect’ was proposed.

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Samples of YBa₂Cu₃O_x in four different phases have been probed by positive muon spin relaxation (μ⁺SR) method. Each phase was found to show different magnetic behavior. In the famous orthorhombic 90 K superconductor (x∼6.9), neither magnetic ordering nor magnetic fluctuations were observed. However, in another orthorhombic superconducting phase (x∼6.4, T_c≈60 K) a magnetic fluctuation was observed below 7 K via muon spin-nuclear spin double relaxation. Its magnetic ordering temperature was expected to be below 2.4 K. Similar behavior was observed in an oxygen-rich (x∼6.5) tetragonal insulating phase, whereas the oxygen-deficient (x∼6.2) tetragonal insulating phase was found to be magnetically ordered, most likely antiferromagnetic, near room temperature. This is the first observation of a magnetically ordered state in the YBa₂Cu₃O_x system.

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Phonon dispersion curves of a high T_c superconductor (La_1−xSr_x)₂CuO₄ have been calculated by making use of the force constants deduced from our experimental results of ultrasonic attenuation and sound velocity for samples (La_1−xSr_x)₂CuO₄ (x=0.07) with T_c∼38 K. Calculations of the dispersion curves of BaPb_1−xBi_xO₃ having a similar crystal structure have also been made to confirm the rightness of the deduction. The results are resumed as follows: the intra-layer optic couplings between Cu and O atoms and between O and O atoms in the coplanar CuO₄ give rise to the energies around 21 meV and 37 meV, respectively, at the Brillouin zone center. These optic phonons with rather small dispersions and with a desirable symmetry property for causing a strong electron-phonon interaction seem to be very favorable to contribute to the high T_c superconductivity.

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Magnetic resonance absorption on CrS_1.17, at frequency of 9.3 GHz, was examined in the temperature range from 150 K to 350 K. A resonance spectrum was observed in all over the ferrimagnetic temperature range, and extremely large g-value, of which the maximum value was 20 at 250 K, was estimated from the result. This anomaly of g-value was explained in terms of Tsuya-Wangsness ferrimagnetic resonance effect. Also, the temperature dependence of resonance line width was explained in terms of the loss mechanism caused upon electron hopping between two types of ions of Cr²⁺ and Cr³⁺ in the material.

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The ground states of quantum spin systems with spin 1/2 are investigated on the triangular lattice by numerically diagonalizing finite size systems (N≤27). In the ferromagnetic and antiferromagnetic XY models the correlation functions are found to decay by power laws. The antiferromagnetic Heisenberg model is likely to be paramagnetic in the ground state. Thus the classical long-range order is destroyed by quantum effects in all of the models we studied.

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Detailed dc magnetic measurements were made on the Cr_1−xMn_xGe alloy system with 0≤x≤0.60 in the temperature range from 4.2 K to 420 K. The alloy system is paramagnetic for 0≤x≤0.06. For 0.09≤x≤0.15 ferromagnetism appears at low temperatures. The system with 0.17≤x≤0.21 shows a dotuble transition from a paramagnetic to a ferromagnetic state at lower temperatures and finally to a mixed phase of ferromagnetic and spin glass ordering. For 0.24≤x≤0.60 spontaneous magnetiztion disappears and a normal spin glass phase is observed. A variety of phase transitions observed in the present alloy system are attributed to the competition between the positive contribution from modified RKKY interaction and the negative contribution from direct exchange interaction to the Mn–Mn exchange interaction.

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The spin-lattice relaxation times T₁ and T_1ρ of protons have been measured in a hexagonal C14 type Laves phase metal hydride ZrCr₂H_4.2 between 4.2 and 333 K. A Korringa type of relaxation due to conduction electrons is obtained as T_1eT=5.01 sec·K, which is about one order of magnitude smaller than 55.6 sec·K in the C15 type Laves phase ZrV₂H₄. T₁ exhibits a minimum owing to the diffusion of hydrogen and an asymmetric variation against 1⁄T about this minimum. The results of T_1ρ measurements show that the asymmetric variation of T₁ is due to a distribution in the activation energy E for the diffusion of hydrogen. The central value and the width of the distribution of E are determined to be 0.29 eV and 0.05 eV, respectively.

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The 4d-4f resonant photoemission spectra for Ce₂O₃ and γ-Ce are analyzed theoretically by using the impurity Anderson model. It is shown that the resonant photoemission can be analyzed consistently with the other photoemission and BIS spectra which were analyzed previously. The difference in the resonance behavior between Ce₂O₃ and γ-Ce is ascribed to the difference in the mixing between f² and f³ configurations in the intermediate state, as well as that between f⁰ and f¹ configurations in the final state. Some discussion is given on the separation of the 4f-derived emission from other symmetry components.

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