[en] The electron-doped bismuth oxide (Ba_0.6Bi_0.4)BiO_2.92 has been successfully synthesized by the two-step heating method. Mixed powders of the starting materials have been pelletized and heated in flowing gas of N₂ at 800 deg. C for 12 h. The reacted pellets have been heated at 400 deg. C first in flowing gas of O₂ for 24 h and then under a high oxygen-pressure of 600 atm at 400 deg. C for 96 h. It has crystallized in a pseudo-cubic symmetry. From the X-ray diffraction and inductively coupled plasma analyses, the substitution of Bi for Ba has been confirmed, but the product has still remained an insulator

[en] In order to study the 1/8 effect in different high-Tc oxides from the La-system, muon spin relaxation measurements were applied to the Zn-substituted Bi-2212 system, Bi₂Sr₂Ca_1-xY_x(Cu_1-yZn_y)₂O_8+δ, around the hole concentration p = 1/8 per Cu. It has been revealed that the magnetic correlation between Cu spins is anomalously enhanced in the Zn-substituted samples at p approximately 1/8 per Cu, proving the existence of the 1/8 effect in the Bi-2212 system as well

[en] We have measured the thermal conductivity κ in the two-dimensional plane of SrCu_2-xZn_x(BO₃)₂ (x=0,0.02) and Cu_3-xZn_xB₂O₆ (x=0,0.03) single-crystals grown by the floating-zone method. It has been found that the temperature dependence of κ exhibits an anomalous peak in the spin-gap state of SrCu₂(BO₃)₂ and also in the antiferromagnetically ordered state of Cu₃B₂O₆. Through the partial substitution of Zn for Cu, the peak does not change in the former, while it is strongly reduced in the latter. It is concluded that the peaks observed in SrCu₂(BO₃)₂ and Cu₃B₂O₆ are caused by the enhancement of κ due to phonons and magnons, respectively

[en] Muon Spin Relaxation Experiments have contributed to understanding the high-temperature superconductivity through (1) Providing the magnetic phase diagram of the copper oxide superconductor, (2) Giving the relation between the condensed electron density n_s and Tc, (3) Clarifying the phase split in the over-dope region, (4) Analyzing the origin of '1/8 abnormality', and (5) Examination of the impurity effect. It is expected that fine variations in the μ SR time spectra can be examined with high intensity muons at J-PARC. Detailed dependency of the spectra on the samples, the temperature and the magnetic fields are also expected to be measured. (K.Y.)

[en] Anomalies in the thermoelectric power and the Hall coefficient, which are analogous to those observed in La_2-xBa_xCuO₄ with x approximately 1/8, have been observed in the Zn-substituted La_2-xSr_xCu_1-yZn_yO₄ with x = 0.115 and y = 0 minus 0.025 and with x = 0.15 and y approximately 0.02. Based on the so-called stripe model, these are explained as being due to the formation of the static order of the stripe-patterned CDW and SDW on account of the pinning by Zn. Accordingly, the long-standing problem on the conspicuous suppression of superconductivity in the Zn-substituted La_2-xSr_xCu_1-yZn_yO₄ with x approximately 0.115 is likely to be attributed to this static order

[en] Highlights: • First superconductor in the Nb-1212 system with the Y-123 type structure is discovered. • Hole-doping is carried out through the partial substitution of Sn⁴⁺ for Nb⁵⁺. • T_c of EuSr₂Cu₂Nb_0.8Sn_0.2O_8−y is about 40 K. -- Abstract: We have successfully synthesized new superconductor EuSr₂Cu₂Nb_1−xSn_xO_8−y of the so-called Nb-1212 system, where Nb is substituted for Cu1 in the RE-123 (RE = rare earth elements) type structure by the hole-doping through the partial substitution of Sn⁴⁺ for Nb⁵⁺. The highest value of the superconductivity of the superconducting transition temperature, T_c, is about 40 K at x = 0.2. This is the first superconductor in the Nb-1212 system

[en] Anisotropic properties of the single crystal Pb₂Sr₂Ho_0.5Ca_0.5Cu₃O₈ have been investigated by measuring the electrical resistivity in the ab-plane ρ_ab(H, θ, T), which depends on the angle θ between the ab-plane and the magnetic-field direction, in various constant fields H perpendicular to the current direction. All the angle-dependent values of ρ_ab(H, θ, T) at a constant temperature are scaled to be on one curve as a function of reduced field. The anisotropic parameter γ triple-bond (m_c*/m_ab*)^1/2 is estimated as 12-13, which is larger than that of YBa₂Cu₃O₇ and much smaller than that of Bi₂Sr₂CaCu₂O₈. It has been concluded that the anisotropy does not always depend on the thickness of the blocking layer but seems to depend on the overlap of the electronic wave functions along the c-axis. Anisotropy in the pinning potential has also been discussed from the resistive tail in the temperature dependence of ρ_ab(H, θ, T)

[en] Li-intercalated layered perovskites Li_xAB₂Na_n-3Nb_nO_3n+1 (A=K, Rb, Cs; B=Ca, Sr, Ba) with n=3 and 4 have been prepared by an electrochemical technique. For the Li_xAB₂Nb₃O₁₀ superconducting materials, the value of T_c has been found to increase up to about 5-6 K as the a-axis length increases. For Li_xCsBa₂Nb₃O₁₀ with the largest a-axis length, however, superconductivity does not appear. In addition, Li_xKCa₂NaNb₄O₁₃ shows no superconductivity

[en] Our recent works on the low-temperature synthesis of oxide superconductors using molten salts are reviewed. We have succeeded in preparing insulating La₂CuO₄ and La_2-x Sm_x CuO₄ with the Nd₂CuO₄-type(T') structure and superconducting (Ba, K, Rb) BiO₃ by the direct precipitation from molten alkaline-metal hydroxides at a low temperature as low as 260-400degC. (author)

[en] Highlights: • First superconductor in the Ta-1212 system with the Y-123 type structure is discovered. • Hole-doping is carried out through the partial substitution of Sn⁴⁺ for Ta⁵⁺. • T_c of EuSr₂Cu₂Ta_0.8Sn_0.2O_8−y is about 40 K. - Abstract: We have successfully synthesized a new superconductor EuSr₂Cu₂Ta_1−xSn_xO_8−y of the so-called Ta-1212 system, where Ta is substituted for Cu(1) in the Y-123 type structure and holes are doped into the CuO₂ plane through the partial substitution of Sn⁴⁺ for Ta⁵⁺. The superconducting transition temperature, T_c, is about 40 K at x = 0.2. This is the first superconductor in the Ta-1212 system