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We find that although T c of Bi 2 Sr 2 Ca(Cu 1−x Co x ) 2 O y (0≤x≤0.1) samples decreases monotonously with increase of x, it increases by 10–30 K upon annealing in vacuum. Inverse photoemission spectroscopy (IPES) result indicates that the intensity of unoccupied O 2p states at Fermi level for the samples is decreased upon annealing. Roles of annealing and Co substitution in the samples are discussed.

The nature of the low frequency plasma in cuprate superconductors and the electromagnetic phenomena related to the plasma excitation are theoretically studied. The interaction of electromagnetic wave with the transverse part of the low frequency plasma causes a peculiar frequency and magnetic field dependence of the reflectivity and transmissivity for a film of cuprate superconductor. It is predicted that the low frequency plasma is excited by the ac Josephson effect.

We theoretically study the vortex states in superconducting multilayers of Nb/NbTi and Nb/NbZr. We solve the Ginzburg-Landau equations numerically and find two different vortex lattices as equilibrium vortex phases. From the free energy calculations, we determine the phase boundary between the vortex phases and map a phase diagram. The magnetization curve exhibits a jump at the phase boundary.

The effects of the substitution of Fe and Co for Cu sites in Bi-2212 samples on T c , lattice parameters, and the electronic structures are studied. The T c and the length of c -axis are monotonously decreased as a function of the amount of Fe and Co. It is found that the Co in Bi 2 Sr 1.8 Ca 1.2 (Cu 1− x Co x ) 2 O y is trivalent and the density of states at the Fermi level is decreased by the substitution. These results are briefly discussed in terms of the disorder effect.

The well characterized surfaces of Ba 1−x K x BiO 3−δ and BaPb x Bi 1−x O 3−δ are investigated by x-ray and ultraviolet photoelectron spectroscopies (XPS and UPS). The clear Fermi edge is found for the fractured surfaces of Ba 0.5 K 0.5 BiO 3−δ and BaPb 0.75 BiO 0.25 O 3−δ using XPS and He l UPS. The valence band shift toward the Fermi level (E F ) by about 0.4 eV with doping K and Pb is observed. The results are compared with the band calculation.

Effects of annealing of Bi 1.6 Pb 0.4 Sr 1.6 La 0.4 CuO x in vacuum on lattice parameters and superconductivity are studied. The amount of evolved oxygen (Δy) is obtained as 6.5×10 −3 by integration of thermal desorption curve of oxygen detected by a mass spectrometer. Upon annealing, the a-axis extends and the T C increases from 22 to 34 K. These results are briefly discussed in terms of redistribution of charge in the system.

The optical conductivity for very low frequencies is investigated in the superconducting state of YBa 2 Cu 3 O 7 using a layered structure model that some pairing interaction generates superconductivity in the CuO 2 -plane layers and the interlayer transfer interaction induces weak superconductivity in the CuO-chain layers. The optical conductivity has contributions from the plane and chain layers which show a striking difference in the temperature dependence below T c . The optical conductivity of the plane layers has a peak just below T c , which is similar to the Hebel-Slichter peak in the nuclear relaxarion rate, and decrease rapidly below the temperature of the peak, while the optical conductivity of the chain layers monotonically increases with desreasing temperature. The temperature dependence of the optical conductivity is compared with that of the nuclear relaxation rate.

We calculate the spin-Knight shifts and the nuclear relaxation rates of the Cu and O ions in the superconducting state of YBa 2 Cu 3 O 7 , using a layer model in which some pairing interaction generates superconductivity in the CuO 2 -plane layers and the interlayer transfer interaction induces weak superconductivity in other layers. If the experimental values of the spin-Knight shift and the nuclear relaxation rate are normalized at T c , these values for the Cu and O ions in each layer are on universal curves in all temperature range of the superconducting state. The normalized spin-Knight shifts and relaxation rates of the Cu and O ions in the plane layer decrease much faster than those in the chain layer in the superconducting state. The present theoretical result well explains the temperature dependence of the normalized spin-Knight shift and nuclear relaxation rate.

Thermal-dilatation measurements on ceramic YBa 2 Cu 3 O 7−δ with various oxygen centrations reveal drift effects of the sample length between 30 and 70K, which are ascribed to thermally activated jump of oxygen atoms.

Nature of the midgap state, which develops in the charge transfer gap of oxide superconductors with hole doping, is studied by use of the p − d mixing model with and without the interatomic short distance Coulomb interaction ( V -term). Composite operators representing electronic excitations associated with Cu-O bonds are introduced and a generalized mean field theory is developed. The doping dependence of the electronic state can be well described by this approach.

The thermal conductivity at T 2 planes in single crystalline YBa 2 Cu 3 O 6.9 can be decomposed as κ a,b ( T ) = κ phonon ( T ) + A·T, while κ c (T) = κ phonon (T). This is explained by a model calculation, assuming that superconductivity is generated in the CuO 2 layers and weak superconductivity is induced in the CUO chains by the proximity effect.

The electronic states near the Fermi level in insulator-metal transition region of p-type oxide superconductors are studied in an effective Hamiltonian obtained from the p-d mixing model. The effective spin-spin interaction induces a tail structure at the top of the occupied p-band and a new narrow band develops with hole doping at the Fermi level, splitting from the main p-band. The obtained effective Hamiltonian seems to describe the change of electronic states even in insulator-metal transition region.

To understand the anomalous temperature dependence of the lower critical field H c1 observed in high-T c copper oxides we use a model of multi-layer structure which is composeo of arrays of superconducting and normal layers. Superconductivity in the normal layers is induced by a proximity effect in this model. The superconducting order parameter on the normal layers is much enhanced at low temperatures. As a result of this enhancement H c1 is drastically enhanced at low temperatures. The calculated results for H c1 explains the anomalous enhancement of H c1 at low temperatures observed in several oxide superconductors.

The electronic states in oxide superconductors are studied in the p-d mixing model by use of the Green’s function method. Due to spin and charge fluctuations induced in the p-d hopping, the electronic states near the Fermi level are modified as follows; 1) the occupied p-band has a tail structure at the top of the band, and 2) a new narrow band develops at the Fermi level inside the charge transfer gap with hole doping. The results seem to explain qualitative behaviours of experiments in photoemission and optical conductivity.

The copper oxide superconductors have layer structures with strongly and weakly superconducting layers. Using the layer structure of YBa 2 Cu 3 O 7 , the tunneling conductance and the specific heat are calculated. The spectrum of the tunneling conductance shows a fine structure inside the superconducting gap at low temperatures in agreement with the results of tunneling experiments. The specific heat has a small electronic contribution even at low temperatures.

We propose new switching gates based on layered structures of high-T c superconductive single crystals. The operation principle of the proposed gate is similar to that of Josephson junction switches but its size is smaller and its speed is faster than those of Josephson junctions. The proposed switching gates consist of a gate current pass parallel to the c-axis of the single crystal. The gate current is controlled by a magnetic flux induced by input current. The area of the gate is less than 1 µ m2. The minimum switching time τ s is estimated as \cong10-13 s. The gate can be used as a memory cell and a flux flow amplifier. As the proposed gate uses a single crystal the noise figure should be low if the crystal used is of high quality.

The anomalous sound attenuation due to spin fluctuations near the magnetic phase transition temperatures in itinerant magnets and the rare earth metals is theoretically studied. By applying Tsuneto and Kadanoff and Falko's formulas, the attenuation coefficient is calculated. The calculated results explain the critical anomalies observed in magnetic metals such as Ni and Gd. By comparing the results with that for insulating magnets, the expression of the exchange striction is obtained. The effect of magnetic field on the critical attenuation is discussed. ferro­ magnets. In this paper, we formulate the attenuation coefficient clue to spin fluc­ tuations and show that the expression of the coefficient in itinerant electron systems is essentially the same as that in localized spin systems. Through this study, the meaning of the exchange strictive interaction in itinerant magnets is clarified. Tsuneto, 8J and Kadanoff and Falko 9J have given an expression for the attenu­ ation coefficient applicable to the system in which the electronic state is strongly modified from the free electron state by impurity and electron-electron interaction. We apply their formula and obtain the critical attenuation coefficients near the magnetic phase transition temperatures in itinerant magnets (§ 2) and the rare earth metals (§ 3). In our formalism, the attenuation coefficient is expressed in terms of the correlation functions of electron-hole pairs. The excitation energy of electron-hole pair is renormalized due to spin fluctuations and the spectral den­ sities at low energies are extremely enhanced near the critical temperature. This enhancement causes the critical attenuation of sound. vVhen the results obtained in §§ 2 and 3 are compared with that of localized spin systems, the meaning of the exchange striction in magnetic metals becomes clear as will be shown in § 4. In the final section (§ 5), the effect of external magnetic field on the attenuation is discussed. In this paper, we neglect the spin­ orbit coupling.

The attenuation coefficient of longitudinal sound waves propagating in ErRh4B4 has been measured as a function of applied magnetic field where the propagation direction (q) of the sound waves was oriented either parallel or perpendicular to Happlied. For both orientations there is evidence of a type II-1 superconducting transition at Hc1 for T ≈ 1.5 K. In addition, when q ⊥ H an increase in attenuation is evident at Hc2, which does not appear when q ‖ H, consistent with theories developed by Tachiki et al. utilizing supercurrent screening of the internal magnetic fields.

Superconducting properties of multilayers composed of a superconductor, a normal metal and a weak ferromagnet are theoretically studied, based on the theory of proximity effect. The physical quantities of the multilayers are calculated taking account of the difference in the densities of states, the diffusion constants, the attractive interaction constants, and the spin susceptibilities of the layering materials. Various behaviors of the upper critical fields which have been observed in the multilayers are explained in a unified manner.

X-ray photoelectron spectra of Ba $3d$ and O $1s$ were measured for BaO, BaC${\mathrm{O}}_{3}$, Ba${(\mathrm{OH})}_{2}$, and $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ in order to elucidate the chemical states of barium in $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$. It is revealed that the photoemission line at 780.4 eV corresponds to ${\mathrm{Ba}}^{2+}$ ions bonded to carbonate and hydroxyl groups, and that at 778.9 eV is due to ${\mathrm{Ba}}^{2+}$ ions in the orthorhombic structure. The O $1s$ lines at 531.2 and 528.4 eV are ascribed to carbonate and/or hydroxyl groups and oxygens in the superconducting oxide, respectively.

The lower and the upper critical fields H c1 and H c2 , and the slope of magnetization at H c2 , (∂ M /∂ H ) c2 , are calculated in ferromagnetic superconductors. The theory takes account of the electromagnetic and the s-f exchange interactions between conduction electrons and localized f-electrons. When temperature decreases, (∂ M /∂ H ) c2 in the mixed state increases and diverges at a certain temperature. This indicates that below this temperature, the transition at H c2 is of a first order. Near the spin ordering temperature, H c2 decreases more rapidly than H c1 with decreasing temperature. The theoretical results are compared with experimental results in single crystals ErRh 4 B 4 in detail.

The electronic state in the metal-insulator transition region of the high T c superconducting oxides is theoretically studied using the d-p mixing model. It is found that a new narrow band arises spontaneously inside the charge transfer gap due to a many body effect, and develops with hole doping. The formation of the band explains many unusual experimental results in the normal state of the oxides.

Effective interaction between localized magnetic moments in ferromagnetic superconductors is studied microscopically by taking account of the interplay among the electromagnetic field, persistent current and magnetic moments. The obtained effective exchange coupling J i j ( q ) can stabilize the spin-spiral ordering with a finite wave number Q , which coexists with superconductivity. By using this J i j ( q ), the spin wave spectrum \(\hbar\omega_{\mbi{q}}\) in the spin-spiral state is calculated at zero temperature. Reflecting a characteristic anisotropy of J j i ( q ), \(\hbar\omega_{\mbi{q}}\) depends strongly on the direction of q ; for q // Q it has a prominent peak at q ∼ Q , but the peak vanishes as q deviates from the Q direction. It is also shown that \(\hbar\omega_{\mbi{q}}\) has many energy gaps characteristic of the magnetic superconductor.

The spin assisted phonon Raman scattering in EuS, EuSe and EuTe is Studied, based on the Raman Polarizability whose spin-phonon dependence originates from the cross effect of the 4 f spin-orbit interaction and the exciton-phonon interction. The phonon dispersions are calculated on the basis of the breathing shell model. The scattering spectrum consists of two parts: One part is a broad line assisted by the spin fluctuations. Most contribution for it comes from LO-phonon, but in EuTe TO-, LA- and TA-phonon contributions also become considerably large. The other part is the sharp line induced by the staggered magnetization. The result of calculation explains the observed results, such as the line shape, and its temperature and magnetic field dependence.

In ferromagnetic superconductors, the spin-spiral phase and the self-induced vortex phase have been predicted to be caused by the interplay between the persistent current and the magnetic moments. Along with these two phases, the Meissner phase, the ferromagnetic normal phase, and the paramagnetic normal phase are also expected to appear in the system. From the calculation of the free energies, the phase-diagrams for these phases are obtained in the planes of temperature-the Landau parameter, -magnetization, and -the concentration of magnetic ions.

A theoretical model is proposed for explaining the anomaly observed in the ultrasonic and specific-heat measurements in the mixed state of ${\mathrm{V}}_{3}$Si. The martensitic transformation in the $A\ensuremath{-}15$ structure compounds causes a drastic change of the electronic structure in the vicinity of the Fermi level, and due to this change the mixed state of the compounds becomes highly anisotropic. The Gibbs free energy, and the lower critical field which depend on the direction of the tetragonal crystal axis relative to an external magnetic field, are calculated by extending the boson theory developed by Umezawa et al. to the case of anisotropic superconductors. The calculation shows that the domains elongated along an applied field in ${\mathrm{V}}_{3}$Si become unstable when the field strength exceeds a critical value. The relation between this instability and the anomaly mentioned above is discussed.

The intensity of the spin assisted Raman scattering in the Eu-chalcogenides is calculated using the excited states which were used in the analysis of the optical absorption. Various mechanisms are examined for the Raman scattering. In these mechanisms, the cross effect of the 4f spin-orbit interaction and the exciton-phonon interaction is found to be the most important for the scattering intensity. The characteristics of the Raman scattering from this mechanism are as follows: When the frequency of the incident light is in the tail region of the absorption peak, the polarization of the scattered light is perpendicular to that of the incident light; when the light in the middle region of the absorption peak is applied, the polarization of the incident light is depolarized in the scattered light; the scattering intensity decreases when the spin fluctuation is suppressed by an application of magnetic field or by lowering temperature through the Curie temperature. These characteristics in the Raman scattering have been observed in the experiments.

Vortex pinning in superlattices composed of the layers of ferromagnetic and nonmagnetic superconductors is studied theoretically. The critical pinning-force density p/sub c/ is calculated as a function of the flux density using the free energy of the mixed state in the superlattices. p/sub c/ is greatly enhanced by the electromagnetic interaction between the vortex current and magnetic moments in the layers of ferromagnetic superconductor. The possibility of high supercurrent capacity in the superlattices is discussed.

In connection with the anomalous temperature dependence of the nuclear relaxation rate $\frac{1}{{T}_{1}}$ of Cu in $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}y}$, the nuclear relaxation in the system is theoretically investigated, and the anomalous temperature dependence is found to be explained on the basis of the Bardeen-Cooper-Schrieffer (BCS) pairing, if the strong correlation effect of electrons is properly taken into account. The spin fluctuations make the superconducting state gapless near ${T}_{c}$ and erase the hump of $\frac{1}{{T}_{1}}$ which is usually observed in BCS superconductors. The spin-fluctuation vertex is highly renormalized in the superconducting state and thus $\frac{1}{{T}_{1}}$, enhanced by the spin fluctuations in the normal state, is drastically suppressed in the superconducting state. The above two effects combined give a sharp decrease of $\frac{1}{{T}_{1}}$ below ${T}_{c}$, which has been observed in the superconducting state of $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}y}$.

A systematic calculation of the Ward-Takahashi identities in 1tmerant electron ferro­ magnetism is presented by making use of the functional integral method. The 1/h-singularity of the magnon Green's function for vanishing energy and momentum plays the significant role. Here h denotes a ficticious infinitesimal magnetic field applied to the system. The identities for the multi point vertex functions corresponding to the processes in which the electron, magnon and longitudinal spin fluctuation interact are given. The electron and magnon pole term contributions to these identities are discussed. § I. Introduction So far a number of theoretical works have been made to clarify the effects of the electron-magnon interaction in itinerant electron ferromagnetism. ll. 2) Any theo­ ry in this field is required to keep the rotational invariance when we make quan­ titative discussion. It is well-known that such invariance is conveniently described in the frame of the Ward-Takahashi identities (hereafter referred to as \VTI). In a previous paper,') we have proposed a systematic approach to calculating WTI in ferromagnetically ordered state making use of the functional integral method. In our treatment, a ficticious infinitesimal magnetic field h is introduced to create the ordered state. h is taken as zero after the end of calculation. The ordered state does not have the spin rotational invariance, and as a result of such breakdown of symmetry, the magnon appears as a Goldstone boson in order to recover the original symmetry. In deriving WTI, the 1/h-singularity of the magnon Green's function for vanishing energy and momentum plays the significant role. The pur­ pose of this paper is to present WTI with the help of the above method for multi point vertex functions in which the electron, magnon (transversal spin fluctuation), and longitudinal spin fluctuation interact with each other and themselves. In order to analyze the electron and magnon propagators, we need at least three point vertex functions which correspond to the magnon emission or absorption

The ternary compounds such as (RE)Rh 4 B 4 and (RE)Mo 6 S 8 contain magnetic rare earth ions RE at the regular lattice sites, nevertheless they show superconductivity. In the superconducting state of films and surfaces of these compounds, the interplay between magnetism and superconductivity causes the following unusual phenomena: the magnetization bound within the London penetration depth from the surface appears below a critical temperature. In the films various types of the magnetic orders coexisting with superconductivity appears depending on the film thickness. The anomalous behavior of the Josephson effect in ferromagnetic superconductors is briefly discussed.

Electron tunneling into ferromagnetic metals is investigated experimentally and theoretically. A large conductance dip centered at the origin is observed for Fe, but for Ni, a smaller dip at the origin appears to be superimposed on a broad peak near the origin. These features may be explained as superimposed elastic and inelastic tunneling effects due to spin waves.

A theory for the Josephson effect in the ferromagnetic superconductors is presented. Taking account of critical fluctuations of the localized-spin magnetization, we calculate the magnetic field dependence of the maximum Josephson current and $I\ensuremath{-}V$ characteristics. The Josephson current is reduced by a noise effect arising from the critical spin fluctuations at low temperatures. The anomalous behaviors observed in the dc Josephson effect in Er${\mathrm{Rh}}_{4}$${\mathrm{B}}_{4}$-${\mathrm{Lu}}_{x}{\mathrm{O}}_{y}$-In junctions are interpreted on the basis of present theory.

We have measured photoemission spectra for Nd 2−x Ce x CuO 4 with and without reduction in order to elucidate the valence-band and Cu 2p core-level electronic structures. We find a density of states at the Fermi level formed by the electrons produced by doping the system with Ce ions. The character of the states is discussed in terms of the resonances and the photon energy dependence. It is suggested that Cu ions doped by electrons have a 3 d 10 configuration since the intensity ratio of the Cu 2p satellites to the Cu 2p 3/2 line decreases as a function of x.

An anomaly has been observed in the ultrasonic attenuation and thermal properties of the $A\ensuremath{-}15$ compound ${\mathrm{V}}_{3}$Si in the superconducting mixed state. The anomalous behavior has been successfully explained in terms of the reorientation of the tetragonal domains, with their $c$-axis perpendicular to the magnetic field. This mechanism of domain instability is based on a model, proposed by Tachiki, one of the present authors, in which an anisotropic mixed state is induced by the band Jahn-Teller effect for the structural (martensitic) transformation just above the superconducting transition temperature. Anisotropic behavior of the ultrasonic anomaly with respect to the direction of an applied magnetic field was studied in order to examine the mechanism. It is found that, although the experimental results are rather complicated due to the demagnetization effect of sample geometry and the irreversible mechanism in nonideal type-II superconductors, they are not contradictory to but qualitatively in agreement with predictions of the model.

The giant thermopower in metals with Ce 3+ impurities is theoretically studied. The relaxation time of a conduction electron is calculated as a function of energy in the selfconsistent ladder approximation by applying Abrikosov's pseudofermion technique to the Coqblin-Schrieffer exchange model with crystal field. The thermopower as well as the electrical resistivity exhibit universal behaviors if the crystal field is neglected. The crystal field induces the characteristic features and the anisotropy in the thermopower versus temperature curve. However, the sign of the thermopower is always positive in Ce system in contrast with Yb systems.

Employing the layer structures of the superconducting copper oxides as intrinsic flux pinning centers, we calculate the critical current density as a function of the direction of an external magnetic field. The critical current Jc has a maximum when the magnetic field is parallel to the CuO2 layer. When the magnetic field is tilted from this layer, Jc drastically decreases. The predicted anisotropy of Jc is in good agreement with that observed by experiments.

Effects of tunneling motion of atoms characteristic in glass systems on superconductivity is theoretically studied. The pair-breaking mechanism of superconductivity proportional to [ln ( T / D )] 2 is derived in the fourth order of the Coulomb interaction between conduction electrons and atoms, where T is the temperature and D is the band width. We propose that the pair-breaking mechanism is an origin of the universal absence of the Maki term in the paraconductivity in amorphous superconductors.

In addition to sharp attenuation peaks of longitudinal sound waves propagating along the [001] axis of a V 3 Si single crystal at the upper critical fields H c 2 , new large attenuation and broad velocity peaks were observed in the mixed state. The new anomaly is explained by a mechanism related to the anisotropy of flux in the crystal tetragonally deformed by the band Jahn-Teller effect.

Anomalous magnetic and superconducting behavior which originates from the electromagnetic interaction between the persistent current and the rare earth magnetic moments is theoretically predicted in thin films of ferromagnetic superconductors. It is shown that the ferromagnetic ordering can coexist with superconductivity for films of thickness smaller than the London penetration depth. The ferromagnetic phase transition is of the second order and its critical temperature depends on the thickness of the film.

The boson theory is reformulated in a form applicable to the mixed state in the rare-earth compounds, $R{\mathrm{Rh}}_{4}{\mathrm{B}}_{4}$, ${R}_{x}{\mathrm{Mo}}_{6}{\mathrm{S}}_{8}$, and ${R}_{x}{\mathrm{Mo}}_{6}{\mathrm{Se}}_{6}$. The magnetic field induced by the persistent current of vortices, and the spin magnetization magnetized by this field are self-consistently calculated. A nonuniform spin magnetization with the periodicity of a flux-line lattice appears in the crystals. The total flux which is the sum of the spin and current contributions is quantized. This quantization effects the current inversion and thus the attractive interaction between the vortices. The calculated magnetization has a tendency of becoming the type-I or type II-1 superconductor even for a large $\ensuremath{\kappa}$. The fact that ${H}_{c2}$ is drastically depressed near the Curie or N\`eel temperature explains the experiments on ${\mathrm{Dy}}_{x}{\mathrm{Mo}}_{6}{\mathrm{S}}_{8}$ and ${\mathrm{Er}}_{x}{\mathrm{Mo}}_{6}{\mathrm{S}}_{8}$.

The dependence of the line shapes on the excitation energy in the Raman scattering (RS) of EuTe at low temperatures is theoretically studied, and is interpreted in terms of the modulation of 5d spin-orbit interaction by lattice displacement. A sharp line induced by the staggered magnetization appears in the vicinity of the absorption edge. This line is observed in off-diagonal Raman polarization configuration. For the incident light with energy near the middle of the exciton absorption, the sharp line disappears and broad line assisted by the magnon excitation appears in both off-diagonal and diagonal polarization configurations. These calculated results are consistent with the experimental result. The RS spectra under a weak magnetic field are also calculated.

The mechanism for the high-T/sub c/ superconductivity in the oxide superconductors is theoretically investigated. The interplay of the Cu-O electron transfer and the Coulomb interaction acting on electrons produces large charge fluctuations with low frequencies in the oxides. The LO phonons strongly interact with the charge fluctuations and generate the Cu-O charge-transfer oscillations with frequencies close to the LO phonons. The amplitudes of the oscillations are extremely large. The experimental results of electron-energy-loss spectroscopy and neutron scattering provide evidence to show the large amplitude of the charge oscillations in the oxides. The interaction mediated by the charge oscillations yields a strong attractive force acting between electrons. We suggest that the attractive force is responsible for the high-T/sub c/ superconductivity in the oxides.

In the experiments for the Josephson effect in the ferromagnetic superconductors such as ErRh4B4, the following anomalous properties have been observed [1,2]. (1) The dc Josephson current disappears at low temperature slightly above the reentrant transition temperature. (2) In the external field dependence of the maximum current (Ic vs. Hex curve) the central peak of the Fraunhofer pattern shifts and splits on cooling just before the Josephson current is quenched.