Nonlinearity parameter is computed for the “Rao liquid”, i.e., a liquid with molecular sound velocity independent of both temperature and pressure, with the result B/A=6. As the Rao liquid is representative of common organic and inorganic liquids excluding highly associated ones, it is concluded that liquids are far more nonlinear than gases for which B/A=γ−1=0.67 at most, where γ means the ratio of the specific heats.

View full abstract

The fracture surfaces of germanium crystals cloven at room temperature have been examined by optical and electron microscopes and also by X-ray diffraction. These observations give evidences that plastic deformation takes place in thin surface zones of fracture surfaces. It is proposed that the surface zones were deformed by imperfect deformation twinning which would take place along {123} Plane in the ideal case. The deviation of the twin boundary from the ideal one is attributed to the high Peierls force in germanium. These deformation twins may be formed through the large stress concentration at the tip of crack. The most significant group of twins is formed along the fracture surface so as to cover it, and the twinning dislocations are created at the tip of crack. Another significant group of twins is formed at the step of crack where large shear stress exists.

View full abstract

The nuclear magnetic resonance of dilute V⁵¹ in Ni–Cu alloys and V⁵¹ in Ni–V alloys was observed in paramagnetic state. The measured Knight shift showed no temperature dependence between 77°K and 300°K whereas some of these alloys had temperature dependent susceptibilities. This behavior is similar to the dilute V⁵¹ Knight shift in palladium.
The magnetic susceptibilities of these alloys were measured and the temperature independent part was obtained by extrapolation to infinite temperature. A linear relationship was found between the temperature independent susceptibility and the V⁵¹ Knight shift for all of these alloys. From the slope of this linear relation, it was revealed that the major part of the change of the V⁵¹ Knight shift is due to the core polarization of vanadium atom induced by the temperature independent paramagnetism of the host metal. These results are interpreted by the model that the vanadium atom hardly feels the magnetic moments of neighboring nickel atoms because of the small susceptibility of the impurity atom resulting from its very deep charge potential in these alloys.

View full abstract

Energy levels of nd transition metal ions in a ligand field of the tetragonal symmetry are studied in the strong field approximation. In this field, d level is split into four sub-levels differing in energy, of symmetry b₁, a₁, e and b₂ respectively. Starting from the configurations containing these orbitals, Coulomb interaction between electrons is introduced, which gives rise to energy levels, each characterized by SΓ. Matrix elements of Coulomb interaction are expressed in terms of Racah’s parameters A, B and C with the ligand field parameters X, Y and Z which give the intervals between orbital energies. These matrix elements are shown for d², d³, d⁴ and d⁵.

View full abstract

A new expression for the energy due to the fluctuation of the magnetization is found for an isotropic continuous ferromagnetic medium. By using the Holstein-Primakoff transformation, it is shown that the terms in this expression except the first term, which was discussed by Herring and Kittel, correspond to spin wave-spin wave interactions, which have the same form as that discussed by Marshall in the energy of spin waves. An expression for the exchange field including the term corresponding to a term of the fourth power of spin wave momentums in the energy of spin waves is found.

View full abstract

The hyperfine field at the Fe⁵⁷ nucleus introduced as an impurity in the nickel lattice has been measured at various temperatures, using the Mössbauer resonance technique. The values follow closely but not exactly the saturation magnetization curve of nickel. No internal field is observed above the Curie temperature of nickel.
The results indicate that the hyperfine field at the impurity nucleus is dependent on the impurity and host magnetic moments in a complex way. The above measurements are compared with the NMR measurements of the temperature variation of the hyperfine field at the Co⁵⁹ and Ni⁶¹ nuclei in nickel. The nonoverlap of these variations are explained qualitatively.

View full abstract

A diagonal component of the magnetoconductivity tensor in graphite at 0°K is calculated as a function of magnetic field from 10⁴ to 2.50×10⁴ gauss by the use of the Slonczewski and Weiss model and the quantum theory of galvanomagnetic phenomena by Adams and Holstein. The Fermi level is calculated in the region of field intensity from 10⁴ to 6.4×10⁴ gauss. The theory is limited to the case 0°K but it is consistent with the features of the measurement made by Soule, McClure and Smith at 1.26°K qualitatively. The scattering potential used in this study is a quasi-delta function with a finite force range of 6°A. For simplicity the trigonal symmetry of the bands (γ₃) is disregarded.

View full abstract

Absorption, excitation and emission spectra and luminescent decay of CsI:Tl have been investigated over the temperature range from 2°K to 300°K. Six absorption bands are observed in contrast with four absorption bands A, B, C, and D in alkali halide-thallium phosphors having the NaCl structure. There exists no other absorption band having a character of the forbidden line as the B band. At 10°K, four emission bands are observed. The luminescent decay is composed of the fast and slow components and is somewhat complicated. For the purpose of comparison, the experiments on CsBr:Tl are also described.

View full abstract

The green edge emission has been studied in cadmium sulfide microcrystallites which deviate from stoichiometry or are doped with NaCl. The spectrum of CdS:S is composed of a doublet structure of emission series; one series beginning at 5147Å is dominant at 77°K and the other beginning at 5178Å is dominant at 4.2°K. The fluorescence in CdS:Cd is complicated. At 77°K, the spectrum is composed of two series of lines, the first series beginning at 5179Å and the second at 5239Å, so that the line structure is rather obscure. At 4.2°K, only the third series beginning at 5178Å appears. CdS: NaCl has two series of lines at 77°K beginning at 5162Å and at 5223Å. At 4.2°K the 5162Å series disappears, while the 5223Å series shifts to the higher energy side by 0.014 eV. The correlations between these emission series of lines and native defects of impurities are discussed.

View full abstract

A calculation is carried out to determine in what way the spin axes vary in the antiferromagnetic domain wall of the NiO-type crystal. The problem can be written in a form of variation calculus to minimize the sum of exchange energy, elastic energy, and magnetic anisotropy energy in the wall region. Dividing the magnetic lattice into four sublattices, the spatial change of spin direction in each sublattice is determined as a function of spatial coordinate for all possible types of the wall. The wall-width and the stored energy in the wall are estimated, using an elastic constant of MnO, to be about 80 Å and 4 erg/cm² for the {001} wall in NiO, and 9 Å and 20 erg/cm² for the {001} wall of MnO. The {110} wall has the width and the energy (1+(J′⁄J))^1⁄2 times as large as those of the {001} wall, where J and J′ are the coefficients of exchange interaction among ⟨100⟩ and ⟨110⟩ neighbours, respectively. In an ideal crystal, such walls are metastable. When a pair of walls is made to approach each other, a pair recombination takes place, and the stored energy in the wall is released to propagate through the crystal.

View full abstract

A general expression of the magnetic anisotropy energy and the magnetoelastic energy in the crystal of magnetic symmetry D_3d is obtained. It is shown that, in NiO, the easy directions of magnetization will be either (Remark: Graphics omitted.) or directions very close to (Remark: Graphics omitted.) when the easy plane is (111), and that, in either case of easy directions, the spontaneous magnetostriction should consist of two strain components representing an orthorhombic deformation and a monoclinic deformation. The magnetoelastic energy is calculated taking four kinds of atomistic origin into account. Contributions from these origins to the energy are shown to be nearly of the same magnitude, and the magnetostrictive strain in NiO is estimated to be of the order of 10⁻⁴ from the calculated energy values and the elastic constants of MgO. Possible directions of magnetic domain walls (S-walls) in such a crystal are predicted from the symmetry of the magnetostrictive strain.

View full abstract

The so-called p-band patterns, i. e., fine lamellar patterns observable within a single T-domain of NiO under a polarizing microscope, have been confirmed, with the use of X-ray techniques, to come from the magnetic domain structure due to the existence of S-walls, whose crystallographic aspects are just as predicted in the preceding paper. From observed behaviours of S-domains in applied magnetic fields, the easy directions of magnetization within the easy plane (111) are determined to be (Remark: Graphics omitted.), but not (Remark: Graphics omitted.). By observing the domain structures with Berg-Barrett method, the magnitude of spontaneous magnetostriction is obtained as |e_x′x′−e_y′y′|=(9±3)×10⁻⁵ and e_z′x′⁄(e_x′x′−e_y′y′)=−0.18±0.06, where the x′-axis is taken along the spin axis, and the z′-axis along [111].

View full abstract

Standing on the band model the experimental data on the Curie temperature and magnetization for Pt metal containing Co and Fe atoms are analysed. It is assumed that 5d-electrons or Pt metal are itinerant and magnetic moments of the dissolved atoms are localized. The results obtained suggest that the values of spin quantum numbers of the localized moments and of the molecular field coefficient between the localized moments and 5d-electrons are not very different from those for Pd metal. The differences between the magnetic properties of Pd and Pt metals containing Co or Fe atoms are mainly due to the difference between the shapes of electronic density of states for these metals.

View full abstract

Rare earth intermetallic compounds in Gd(Ag, Cd, In) and Gd(Cu, Ag, Au) systems have been studied. Most of these compounds have the CsCl type of crystal structure. Magnetization measurements have been made on these compounds to determine the type of the magnetic order and its relationship to the number of conduction electrons. GdAg, GdAg_0.9In_0.1, GdAg_0.2In_0.8, GdAg_0.1In_0.9, and GdIn in the Gd(Ag, In) system and GdCu, GdAg, GdAg_0.7Au_0.3, and GdAg_0.5Au_0.5 in the Gd(Cu, Ag, Au) system are antiferromagnetic at low temperatures. On the contrary, GdCd, GdAg_0.8In_0.2, GdAg_0.7In_0.3, GdAg_0.5In_0.5, and GdAg_0.3In_0.7 are ferromagnetic at low temperatures. GdCd has a very high Curie temperature of 262°K. In the Gd(Cu, Ag, Au) system, the Néel temperature increases with the increase in the lattice constant. The remarkable difference in magnetic behavior between the Gd(Ag, Cd, In) system and the Gd(Cu, Ag, Au) system is considered to be associated with the fact that the number of conduction electrons plays more important role in determining the magnetic behaviors than the interatomic separation.

View full abstract

Earlier experimental work (J. Ferguson, H. J. Guggenheim and Y. Tanabe, J. appl. Phys. 36 (1965) 1046, Phys. Rev. Letters 14 (1965) 737) on the Mn pair spectrum of KZnF₃:Mn and the spectrum of KMnF₃ has been extended. The narrow bands of KMnF₃ and RbMnF₃ have been assigned and their abnormally high intensities established. The transition is an electric dipole one and oscillator strength (∼9.5×10⁻⁷ for the 4000 Å absorption) is temperature independent, corresponding to an allowed transition.
The experimentally observed features of the pair absorption suggest a possible form of interaction between radiation and paramagnetic ion pair. The origin of this interaction is discussed and an order of magnitude argument is given to support the proposed mechanism. Related problems such as exchange interaction in excited states and the spectra of the concentrated materials are also considered.

View full abstract

The Morigaki-Hoshina’s model of the optical quenching bands in ESR signal due to the Fe³⁺ ions in CdS was examined and confirmed through photoconductivity measurements at 4.2°K. The observation of corresponding quenching bands in photoconductivity suggests that the bonding level t₂^b should be immersed into the valence band or at least lie at 0.1 meV or near above it. From the features of photoresponse, the presence of the deep lying electron-ejectable centers is concluded in the forbidden gap. The result of photoconductivity measurements in microwave region is also presented which seems to support the results in the d. c. case.

View full abstract

The Mössbauer spectra of Fe⁵⁷ in FeGe were measured over the temperature range from 79°K to 413°K. The hyperfine field due to the antiferromagnetic ordering was observed. Its value at 79°K was 155 kOe. The Néel point as determined from the temperature dependence of the internal magnetic field was 400°K. The isomer shift at room temperature was +0.22 mm/s. relative to pure Fe and varied with temperature like that of Fe. The electric quadrupole splitting (Remark: Graphics omitted.) was +0.35 mm/sec at room temperature.

View full abstract

Infrared absorption in p-type semiconductors due to the transitions from split off valence bands to shallow acceptor states and to heavy and light hole bands was investigated in terms of k–π perturbation approach. Contrary to the case of germanium (diamond type), transitions from the split off valence bands to the top valence bands are allowed at Γ point in the zincblende structure. Although the contribution of the π matrix elements between Γ_7v and Γ_8v states to the absorption cross section is not large compared with that due to the k–π perturbed parts of wave functions in GaAs, they are of comparable magnitude in ZnTe. The radii of shallow acceptor states are determined to be 26 and 10 Å respectively for Ge and ZnTe, by fitting the formulas derived here to experimental data. In the case of ZnTe, the change of absorption curve relative to photon energy with increasing temperature may be attributed to the increasing contributions of inter-valence band transitions.

View full abstract

The resistivities and the magnetic susceptibilities of lanthanum containing small amounts of other rare-earth metals have been measured at low temperatures. Resistance minima have been found at about 6.5°K in fcc La–Ce alloys and at about 5.8°K in hcp La–Ce alloys. The temperature at which the resistance minimum occurs is independent of the concentration of Ce. Any minimum has not been found in the alloys with solutes other than Ce. The observed resistivity of all the alloys contains a term proportional to logT in accordance with the recent theories on the s-d or s-f resistivity due to Kondo and others. The magnetic susceptibilities of La–Ce, La–Pr, and La–Nd alloys are not inconsistent with the resistive behaviors of these alloys. The effective s-f exchange integrals for various rare-earth solutes have been calculated from the resistivity data and compared with those calculated from the change of the superconducting transition temperature of La due to added rare-earth metals. The agreement between the two is not good for heavy rare-earth solutes. The increment in the residual resistivity of La due to the solute seems to be explained mostly by the magnetic scattering.

View full abstract

Magnetization curves along the c-axis of natural pyrrhotite crystal (Fe₇S₈) are measured in high magnetic field (up to about 100 kOe) from room temperature down to liquid helium temperature. By means of the X-ray method, it is also confirmed that the ordered arrangement of vacant sites and ions has no temperature dependence in the range from 80°K to 300K°. The magnetic results are well explained on the basis of Adachi’s theory that the magnetocrystalline anisotropy is caused by the ordered arrangement of vacant sites, and ferric and ferrous ions.

View full abstract

The present paper describes the formation process of a rotating plasma in a homopolar-like short coaxial-electrode system carried out in a H₂, N₂ or A discharge. A Kerr cell shutter with a 50 ns exposure time was used for optical records. It is found that the process is divided into two stages: first a negative streamer appears and develops to a spoke, and later the spoke spreads to a disk. The streamer process is hardly affected by the magnetic field. A plausible mechanism by which the spoke spreads to the disk is ionization of neutrals by E×B drift motion of ions. There is a critical gas pressure above which the spoke never spreads to the disk. The reason is considered to be that ions cannot drift in E×B direction above the critical pressure due to a large frictional force between ions and neutrals.

View full abstract

The plasma-ion oscillations were observed in a diode-type discharge tube varying the longitudinal magnetic field or the cathode temperature. When the magnetic field strength was increased, the oscillation frequency increased up to a critical value at constant discharge current and the oscillation disappeared at higher magnetic fields. A similar variation in the oscillation was observed when the cathode temperature was decreased. These frequency shifts are qualitatively explained. Considering the electron drift velocity, the excitation mechanism of the plasma-ion oscillation is also discussed using the theory by Fried and Gould.

View full abstract

Relaxation of the distribution function of ions confined in a mirror field is in investigated theoretically taking both the charge exchange and scattering effects into account. The result is compared with experiment.
If the particles are not thermalized sufficiently, the ion density decays exponentially due to the charge exchange, but only linearly due to the mirror loss. The life time, τ_cx, is proportional to the ion velocity while that of the mirror loss, τ_m, is proportional to it to the power three.
The experiment is performed on the HX-0 device, a mirror machine for high temperature experiments. A decay time of 26 μs is obtained for high energy protons which are trapped in the mirror magnetic field at the background pressure of 10⁻⁵mm Hg.

View full abstract

Non-linear ion acoustic waves propagating in a plasma of warm electrons and one or more streams of cold ions are investigated. A hydrodynamical model which employs ion fluid streams interacting among themselves through the electron pressure gradient is used, isothermal electrons being assumed. Though the present model assumes charge neutrality, it enables us to show how large amplitude disturbances become steeper, tending to form shocks or inversely how discontinuous initial disturbances are smoothed out. For a single fluid, the behaviour is the same as those of isentropic gas with γ equal to unity. However for multicomponent cases there exist conspicuous properties such as multi-stream instabilities. This paper discusses all these effects for the case of two streams. Simple waves are obtained by means of the method of characteristics; for the wave propagating faster than all the ions the compression leads to shock formation whilst the expansion to the instability, for the waves lower than all the ions the expansion leads to the shock formation and at the same time to instability and for the wave propagating with intermediate speed the situation is more complicated.

View full abstract

The propagation of hydromagnetic waves in collisionless plasma is investigated on the basis of the Chew-Goldberger-Low approximation. The dispersion relation for weak, plane disturbances in a uniform plasma is derived. It is found that there exist the fast and slow modes of magnetoacoustic waves as well as the Alfvén wave. However, under certain conditions the phase velocities of the slow and the Alfvén waves become imaginary: namely the system is not necessarily totally hyperbolic but can be partially elliptic. The conditions on the elliptic cases are investigated in detail, especially for the slow wave. Then the propagation of a wave diverging from a point source is investigated graphically as well as analytically.
The general theory of steady flow is also given, and some discussions are done for the two dimensional aligned field-flow in which the directions of magnetic field and flow are aligned everywhere.

View full abstract

A possibility of amplification by a cylindrical cavity of reflection type coaxial with a plasma column along the static magnetic field is discussed. The Q-value contributed from the plasma (Q_p) is calculated under the following conditions: i) The plasma is so tenuous that the perturbation theory may be used. ii) The velocity distribution function for plasma electrons is f₀∝v^qexp(−bv^s). iii) The effective collision frequency for momentum transfer is dominantly due to the collisions of an electron with neutral particles and varies with the speed v as ν_c(v)∝v^h. iv) The radius of the plasma is sufficiently smaller than the radius of the cavity.
When Q_p<0, the plasma-cavity system has a possibility of amplification or oscillation. This characteristic depends sensibly on the velocity distribution function for plasma electrons.

View full abstract

An investigation is made of the propagation of electromagnetic waves normal to a plasma slab having a density gradient. The plane of polarization of waves is perpendicular to an external magnetic field. At resonances, a WKB-type approximation does not represent waves and an appreciable absorption appears due to infinitesimal collisions: the so called resonance absorption. The transmission and absorption coefficients are obtained in the limit of no collisions when in the slab the cut off is adjacent to the resonance.

View full abstract

The slip flow of an electrically conducting viscous fluid over a porous flat plate under uniform transverse magnetic field is investigated. The external velocity is time dependent and the cases of impulsive free stream and accelerated free stream are considered in detail. It is found that the velocity increases with slip parameter \sqrtε while the skin friction and displacement thickness decrease with it. The graphs drawn indicate that the analysis is not applicable beyond certain value of \sqrtε.

View full abstract

An attempt is made to study the effects of elastico-viscosity and cross-viscosity of a Second-order fluid on its advancement over an infinite flat plate. The cross-viscous forces modify the pressure but do not alter the boundary layer thickness or the velocity profile. The elastico-viscous effect is shown to depend upon a dimensionless parameter K. Numerical computation shows that an increase in elastico-viscosity of the fluid increases the boundary layer thickness and skin friction on the plate.

View full abstract