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The irreversibility field Hirr and the anomalous second peak in the magnetization curves have been studied from the magnetization measurements (H || c-axis) for Pb2Sr2Y1−xCaxCu3O8 single crystals with 0 ≦ x ≦ 0.5 and with the anisotropic parameter γ ≡ (mc∗/mab∗)12 of 24 ≧ γ ≧ 5. The temperature dependence of Hirr is discussed in terms of flux creep and 2D or 3D vortex-lattice melting. The anomalous second peak is observed for all x values. The peak shape is similar to that of YBa2Cu3O7−δ. The peak field Hp is dependent on temperature and proportional to (1 − T/Tc)32 near Tc. Both Hirr and Hp at each reduced temperature are proportional to γ−2 the origin of the second peak is discussed in terms of dimensional crossover of the vortices from 3D to 2D and collective pinning.

Changes of the dimensionality and Tc through iodine intercalation and oxidation have been studied in Bi2Sr2CaCu2O8+δ single crystals. Both intercalation and oxidation change the dimensionality of the physical properties from pseudo-two-dimensional to three-dimensional and decrease Tc. These effects are explained by the multilayer model, where a high-Tc cuprate is regarded as an alternating stack of CuO2 layers (superconducting layers) and block layers (normal layers), taking into account the proximity effect. The Tc-suppression by Cu-site substitution has also been studied for iodine-intercalated and pristine Bi2Sr2Ca(Cu1−zCoz)2O8+δ polycrystals with different δ-values.

Anisotropie properties of the single crystal Pb2Sr2Ho0.5Ca0.5Cu3O8 have been investigated by measuring the electrical resistivity in theab-planeρ ab (H, θ,T), which depends on the angleθ between theab-plane and the magnetic-field direction, in various constant fieldsH perpendicular to the current direction. All the angle-dependent values ofρ 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≡(m * /m * )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 thec-axis. Anisotropy in the pinning potential has also been discussed from the resistive tail in the temperature dependence ofρ ab (H,θ,T).

Anisotropic properties of the electrical resistivity and the resistive superconducting transition under magnetic fields have been investigated for the single-crystal Pb 2 Sr 2 Y 1− x Ca x Cu 3 O 8 with 0 ≦ x ≦ 0.5 in the so-called underdoped region. The anisotropic parameter γ ≡ (m ∗ c /m ∗ ab ) 1 2 is found to increase from ∼5 to 25 with decreasing x , namely, with decreasing hole concentration. The irreversibility field H irr has been studied from the magnetization measurements for H ⋎ c- axis . In the high-temperature regime near T c , H irr is found to be proportional to 1−T/T c ) 3 2 for x ∼0.5 and to (1−T/T c ) 3 2 or (1− T / T c ) 2 for smaller x values. In this regime, H irr is also found to be proportional to γ −2 . In the low-temperature regime, on the other hand, H irr grows exponentially as approximately expressed as e − T / T o , and shows a still stronger growth as e T o / T at much lower temperatures for smaller x values. These behaviors are discussed in terms of flux creep, vortex-lattice melting and vortex-glass melting.

The superconductivity and intercalation state in the lithium- and hexamethylenediamine (HMDA)-intercalated superconductor Lix(C6H16N2)yFe2−zSe2 have been investigated from powder x-ray diffraction, thermogravimetric, and magnetic susceptibility measurements, changing the intercalation temperature Ti and the Li content x. Both Li and HMDA have been co-intercalated stably up to x = 2 roughly in a molar ratio of \(x:y = 2:1\). In the case of Ti = 45 °C, it has been found that both Li and HMDA are co-intercalated locally at the edge of FeSe crystals, indicating that both Li and HMDA are hard to diffuse into the inside of FeSe crystals at 45 °C. In the case of Ti = 100 °C, on the other hand, it has been found that both Li and HMDA diffuse into the inside of FeSe crystals, so that Tc tends to increase with increasing x from ∼30 K at x = 1 up to 38 K at x = 2 owing to the increase in the number of electron carriers doped from Li into the FeSe layers.

New FeSe-based intercalation superconductors, Ax(C8H11N)yFe1−zSe (A = Li, Na), with Tc = 39–44 K have been successfully synthesized via the intercalation of alkali metals and 2-phenethylamine into FeSe. The interlayer spacings, namely, the distances between neighboring Fe layers, d, of Ax(C8H11N)yFe1−zSe (A = Li, Na) are 19.04(6) and 18.0(1) A, respectively. These d values are the largest among those of the FeSe-based intercalation compounds and are understood to be due to the intercalation of two molecules of 2-phenethylamine in series perpendicular to the FeSe layers. It appears that the relationship between Tc and d in the FeSe-based intercalation superconductors is not domic but Tc is saturated at ∼45 K, which is comparable to the Tc values of single-layer FeSe films, for d ≥ 9 A.

The ${\mathit{T}}_{\mathit{c}}$ suppression by Cu-site substitution has been studied in a wide range of carrier concentrations p, from the underdoped regime to the overdoped regime, using sintered polycrystals of ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{Ca}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Y}}_{\mathit{x}}$(${\mathrm{Cu}}_{1\mathrm{\ensuremath{-}}\mathit{z}}$${\mathit{M}}_{\mathit{z}}$${)}_{2}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ with x=0 and x=0.3 and under variation of \ensuremath{\delta}. The carrier-dependent strength of the ${\mathit{T}}_{\mathit{c}}$ suppression by substituting M=Fe, Co, Ni, Zn for Cu is measured. In the overdoped regime, we find ${\mathit{T}}_{\mathit{c}}$ scaling as ${\mathit{T}}_{\mathit{c}}$(p,z)/${\mathit{T}}_{\mathit{c}}$(p,0)=g(z) with a p-independent function g(z), whereas in the underdoped regime ${\mathit{T}}_{\mathit{c}}$(p,z)/${\mathit{T}}_{\mathit{c}}$(p,0) is strongly p dependent. Replotting data of various publications on the ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{4}$ system and comparison with the ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ system demonstrate the universality of this distinction between the two regimes in p-type high-${\mathit{T}}_{\mathit{c}}$ cuprates. The scaling behavior is discussed with respect to Born-limit and unitarity-limit scattering.

We have investigated the effects of extra oxygen on the crystal structure, transport properties and superconductivity in the Pb3201 phase of (Pb 2 Cu)Sr 9 La 1.1 CuO 6+δ prepared by the polymerized complex method. A structural phase transition from orthorhombic to tetragonal phase is observed with increasing δ. The sample is orthorhombic for 0 ≲ δ ≲ 0.4, tetragonal for 1.7 ≲ δ ≲ 2 and a mixture of the orthorhombic and tetragonal phasse for 0.4 ≲ δ ≲ 1.7. In the orthorhombic phase of δ ≲ 0.3−0.4, T c increases with increasing δ, owing to the increase of holes in the CuO 2 sheets from the extra oxygen. In the tetragonal phase, on the other hand, the superconductivity disappears on account of the small hole concentration in the CuO 2 sheets, owing to the increase of the Pb valence from +2 to +4.

Post-annealing effects on the crystal structure and superconductivity of the lithium- and hexamethylenediamine (HMDA)-intercalated superconductor Lix(C6H16N2)yFe2-zSe2 have been investigated. Through the post-annealing, a two-step reduction of the interlayer spacing between neighboring Fe layers, d, has been observed. It has been found that a new phase of Lix(C6H16N2)yFe2-zSe2 with d= 10.30(2) {\AA} and Tc = 41 K different from the as-intercalated phase is stabilized owing to the possible stable inclination of HMDA intercalated between FeSe layers. This result supports the domic relation between Tc and d in the FeSe-based intercalation superconductors. The reason why Tc increases with a decrease in d through the post-annealing is discussed., Comment: 12 pages, 6 figures

The dependence of the superconducting transition temperature T c on the excess oxygen content δ has been investigated for Bi 2 >Sr 2 >CaCu 2 >O 8+δ annealed under high pressures of oxygen. With increasing δ, T c decreases for δ≲0.3 and then becomes constant for δ≳0.3. It has been found by chemical titration that this strange δ dependence of T c is related to the δ dependence of the average valency of Cu ions. That is, the average valency increases with increasing δ for δ≲0.3 and then is saturated for δ≳0.3. For δ≳0.3, the Curie-Weiss component in the DC magnetic susceptability has been found to increase with increasing δ. Therefore, the saturation is ascribed to the fact that most of the excess oxygen atoms exceeding δ≈0.3 are introduced in the form of O 2 instead of O 2- .

We have succeeded in synthesizing a new intercalation compound Bi2Sr2(Gd0.82Ce0.18)2Cu2O10+δI with stage-1 structure. The increase in spacing between the BiO-BiO double layers through the iodine intercalation is 3.7 A. The electrical resistivity and superconductivity have been investigated for iodine-intercalated samples of Bi2Sr2(Gd0.82Ce0.18)2Cu2O10+δIx with 0≦x≦1 and bromine-intercalated ones of Bi2Sr2(Gd0.82Ce0.18)2Cu2O10+δBrx with 0≦x⪅0.2. It has been found that non- superconducting assintered samples of Bi2Sr2(Gd0.82Ce0.18)2Cu2O10+δ become superconducting at low temperatures below about 20 K through the light bromine intercalation. This suggests that the role of annealing under high pressures of oxygen in the appearance of superconductivity for the Bi-2222 phase is to supply the CuO2 sheets with enough hole carriers.

We have investigated the stage-1 iodine-intercalation compounds, whose host materials are Bi2Sr2Ca1−x Y x Cu2O8 (Bi-2212 phase) and Bi1.6Pb0.5Sr1.9−x La x Cu1.05O6 (Bi-2201 phase) with variousx values. In the Bi-2212 phase, it has been found that the change inT c through the stage-1 iodine intercalation is due to two effects; a change of the two-dimensionality and an increase in the carrier number. The former effect decreasesT c by about 10 K independent of the carrier number of the host sample. The latter effect shifts thex dependence ofT c to largerx values by about 0.08, taking account of oxygen release from the host samples during the intercalation process. This result is clear evidence for the occurrence of both the change of two-dimensionality and the increase in carrier number about 0.04 per CuO2 unit due to the charge transfer through the stage-1 iodine intercalation. In the Bi-2201 phase,T c decreases by about 10 K through the stage-1 iodine intercalation.

The electronic specific heat of as-grown and annealed single-crystals of FeSe1-xTex (0.6, Comment: 22 pages, 1 table, 6 figures, Version 2 has been accepted for publication in J. Phys. Soc. Jpn

The relationship between the crystal structure and superconductivity has been investigated for La 1.9 Bi 0.1 CuO 4+δ with excess oxygen. A phase diagram in the T -δ plane is given for this system, where the phase separation observed in La 2 CuO 4+δ is suppressed. For very small values of δ the crystal structure is orthorhombic, and an orthorhombic-tetragonal phase transition occurs markedly at δ∼0.03 in the measured temperature range between 13 and 293 K. A superconducting phase is observed in the range of 0.04≤δ≤0.11. This is clear evidence that high- T c superconductivity also appears in the tetragonal phase.

We have succeeded in synthesizing a new intercalation compound of Bi 2 Sr 2 CaCu 2 O 8 (IBr) 1 2 with the stage-1 structure. The increase in spacing between the BiO-BiO double layers through IBr intercalation is 2.1 A, which is a little larger than the 2.0 A in the case of Br intercalation alone and is smaller than the 3.5 A in the case of only iodine intercalation. The superconducting transition temperature T c of Bi 2 Sr 2 CaCu 2 O 8 (IBr) 1 2 decreases with increasing x for 0 ≦×⪅0.4 and is almost constant, 55 K, for x⪆0.4. This x dependence of T c is very similar to those of Bi 2 Sr 2 CaCu 2 O 8 Br x and Bi 2 Sr 2 CaCu 2 O 8 I x . This is discussed in relation to the changes of the two-dimensionality and hole concentration in the CuO 2 sheets through intercalation. A trial of ICl intercalation into Bi 2 Sr 2 CaCu 2 O 8 is also described.

Site preference of the partially substituted 3d metal M and superconducting and magnetic properties have been investigated for Pb2Sr2Y1 − xCax(Cu1 − yMy)3O8 (M = Fe, Co, Ni, Zn, Ga). It has been found from powder neutron diffraction that Fe atoms preferentially occupy the Cu(1) site in the oxygen-free Cu layer, while Co, Ni, Zn and Ga atoms occupy the Cu(2) site in the CuO2 layer. From correlation between this site preference of M and the superconducting and magnetic properties, it has been concluded that the partial Cu(1)-site substitution shows little effect on the superconductivity and that there remains antiferromagnetic correlation between Cu2+ spins in the Cu(2) site in the normal state even for the high-Tc samples of x = 0.5 with Tc ≈ 80 K.

Variations of the crystal structure and superconductivity with iodine concentration have been investigated for iodine-intercalated sintered-samples of Bi 2 Sr 2 CaCu 2 O 8 I x with 0≦ x ≦1. It has been found from powder X-ray diffraction that samples with 0.4≲ x ≲0.7 are composed of mixed phases of the host compound Bi 2 Sr 2 CaCu 2 O 8 and the stage-1 iodine-intercalation compound Bi 2 Sr 2 CaCu 2 O 8 I. Diffraction peaks due to the stage-3 structure are vaguely observed for a sample with x =0.24. In spite of the mixed-phase structure for 0.4≲ x ≲0.7, the superconducting phase is single and of the bulk for all x values. The superconducting transition temperature decreases with increasing x for 0≦ x ≲0.4 and is almost constant for 0.4≲ x ≦1. A model of the x dependence of the spatial distribution of intercalated iodine atoms is proposed, and the x dependence of T c is discussed in relation to that of the charge transfer between iodine atoms and the CuO 2 sheets.

Effects of the stage-1 iodine-intercalation on T c have been investigated in Bi 2 Sr 2 Ca 1− x Y x Cu 2 O 8 . The iodine intercalation produces two large effects; one is enhancement of the two-dimensionality due to expansion of the crystal along the c -axis, and the other is increase of conductive hole carriers due to charge transfer between intercalated iodine atoms and CuO 2 sheets in the host material. For the stage-1 iodine-intercalation compounds, it has been found that the former effect decreases T c by about 10 K and that the latter effect shifts the x dependence of T c to larger x values by about 0.05 because of the increase of conductive hole carriers by about 0.025 per CuO 2 unit. It has been concluded that the decrease in T c through the I intercalation in Bi 2 Sr 2 CaCu 2 O 8 is due to both effects.

Effects of the 1% substitution of Ni, Zn and Ga for Cu on the x dependence of Tc have been investigated in La2−xSrxCuO4. The Tc increases by the Cu-site substitution in all compositions of x. The local minimum of Tc as a function of x, appearing slightly near x = 0.115 for La2−xSrxCuO4, becomes conspicuous with decreasing Tc. However, structural phase transition from the orthorhombic mid-temperature phase to the tetragonal low-temperature phase has not been detected from powder X-ray diffraction measurements at low temperatures down to 12 K. The local minimum of Tc is attributable to the fluctuation of the undiscovered structural phase transition, which will occur at a low temperature below 12 K as long as samples are in the normal-conducting state. In the 1% Ga-substituted system for Cu, the local minimum clearly shifts from x = 0.115 to 0.125. This suggests that the undiscovered low-temperature structural phase transition is due to the optimum hole concentration of 0.115 per Cu atom, analogously to La2−xBaxCuO4.

A trial of carrier doping into Ca 1− x Sr x CuO 2 has been made through partial substitution by conventional solid-state reaction under ambient pressure. The element Y or Na has been taken for the Ca-site substitution, Ga or Li for the Cu site, and F for the O site. It is hard to carry out hole doping into Ca 1− x Sr x CuO 2 . As for electron doping, electron carriers are most doped in samples within the solid-solution limit of y ≈0.05 in Ca 0.86− y Sr 0.14 Y y CuO 2 , but the carrier concentration estimated from the Hall coefficient is still too small to bring superconductivity. Almost all of the samples remain semiconductor-like and no samples show superconductivity of the bulk above 4.2 K. These results are discussed in relation to the oxygen stoichiometry and the Madelung potential. In addition, resistive and magnetic anomalies observed at about 50 K in several samples of Ca 0.82 Sr 0.16 Y 0.02 CuO 2 are described.

Intercalation of Br and Li into Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 ( n = 1, 2, 3) has been tried. For heavily Br-intercalated samples of n = 2 and 3 with x ≈ 1 in Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 Br x , enlargement of the c-axis is detected, suggesting that intercalation compounds Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 Br with Br atoms between double BiO layers are synthesized. For Li-intercalated samples, on the other hand, clear evidence to show the formation of intercalation compounds is not obtained. For lightly Br- and Li- intercalated samples of n = 1, 2, 3, changes of the electrical resistivity, the Hall coefficient and T c by the intercalation are observed, which are attributable to charge transfer between intercalants and CuO 2 planes in the host materials Bi 2 Sr 2 Ca n−1 Cu n O 2n+4 . That is, the intercalation of Br and Li is effective for hole and electron doping into CuO 2 planes, respectively. For n = 3, T c decreases by the light intercalation of both Br and Li, suggesting that Bi 2 Sr 2 Ca 2 Cu 3 O 10 has almost optimum hole concentration to attain the maximum of T c .

Effects of the partial substitution of Ce for La on the superconductivity and the low-temperature structural phase transition have been investigated in La2-xBaxCuO4. The local minimum of Tc as a function of Ba concentration x, appearing near x = 0.125 for La2-xBaxCuO4, clearly shifts to x = 0.145 for La1.98-xCe0.02BaxCuO4. The range of x, where a resistance minimum relating to the low-temperature structural phase transition appears, shifts to that of larger x values, too. These suggest that the low-temperature structural phase transition around x = 0.125 in La2-xBaxCuO4 is due to the optimum hole concentration of 0.125 per Cu atom rather than plausible atomic ordering of La and Ba.

Effects of the partial substitution of Ni, Zn and Ga for Cu on the anomalous x dependence of Tc and the resistance anomaly around 60 K have been investigated in La2−xBaxCuO4. Tc decreases by the substitution in comparison with non-subsituted samples in almost all compositions of x except compositions near x = 0.125. For 1% Ga-substituted samples for Cu, the local minimum of Tc as a function of x, appearing near x = 0.125 for non-substituted samples, clearly shifts to x ≈ 0.135. This suggests that the low-temperature structural phase transition around x = 0.125 in La2−xBaxCuO4 is primarily due to the optimum hole concentration of 0.125 per Cu atom rather than the atomic ordering of La and Ba. The resistance anomaly near 60 K does not change clearly by the substitution.

We have measured the thermal conductivity of the one-dimensional (1D) S =1/2 Heisenberg antiferromagnetic spin system of Sr 2 Cu 1- x Pd x O 3 single crystals including nonmagnetic impurities of Pd 2+ . It has been found that the mean free path of spinons along the 1D spin chain at low temperatures is very close to the average length of finite spin chains between spin defects estimated from the magnetic susceptibility measurements. This proves that the thermal conduction due to spinons at low temperatures in Sr 2 CuO 3 is ballistic as theoretically expected [Zotos et al. : Phys. Rev. Lett. 55 (1997) 11029].

Cord serum concentrations of the N-terminal propeptide of type-III procollagen(PIIIP), insulin-like growth factor I (IGF-I), thyroid-stimulating hormone (TSH) and free thyroxine were measured in 149 neonates, consisting of 22 small for gestational age, 95 appropriate for gestational age, 21 large for gestational age and 11 neonates of less than 24 weeks of gestation. Their gestational ages (GAs) ranged from 20 to 41 weeks. A significant negative correlation was found between PIIIP levels and GA (r = ––0.83, p < 0.001). No significant difference was found in PIIIP levels between SGA and LGA neonates, when there were no difference in their GAs, in spite of a significant difference in their birth body weights (p < 0.01). The high concentrations of the cord serum PIIIP did not appear to be influenced by either IGF-I or thyroid hormones, nor was there any relationship between PIIIP and the birth body weight, but only with GA, suggesting that determining cord levels of PIIIP seems to provide a useful parameter for the assessment of newborn maturity.

In order to investigate the inhomogeneity of the superconducting (SC) state in the overdoped high-$T_{\rm c}$ cuprates, we have measured the magnetic susceptibility, $\chi$, of La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) single crystals in the overdoped regime in magnetic fields parallel to the c-axis up to 7 T on warming after zero-field cooling. It has been found for $x$ = 0.198 and 0.219 that the temperature dependence of $\chi$ in 1 T shows a plateau, that is, $\chi$ is almost independent of temperature in a moderate temperature-range in the SC state. Moreover, a so-called second peak in the magnetization curve has markedly appeared in these crystals. These results indicate an anomalous enhancement of the vortex pinning and strongly suggest the occurrence of a $microscopic$ phase separation into SC and normal-state regions in the overdoped high-$T_{\rm c}$ cuprates., Comment: 4 pages, 4 figures

We have successfully synthesized well-crystallized bulk samples of La2CuO4 with the Nd2CuO4-type structure by the direct precipitation from the molten KOH/NaOH eutectic mixture including La2O3 and ...

${\mathrm{Ta}}_{2}{\mathrm{S}}_{2}\mathrm{C}$ compound undergoes superconducting transitions at ${T}_{\mathit{cl}}=3.60\ifmmode\pm\else\textpm\fi{}0.02\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and ${T}_{\mathit{cu}}=9.0\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The nature of successive superconducting transitions has been studied from electrical resistivity and linear and nonlinear ac magnetic susceptibilities. The resistivity $\ensuremath{\rho}$ at $H=0$ shows a local maximum near ${T}_{\mathit{cu}}$, a kinklike behavior around ${T}_{\mathit{cl}}$, and reduces to zero at below ${T}_{0}=2.1\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The $\mathrm{ln}\phantom{\rule{0.2em}{0ex}}T$ dependence of $\ensuremath{\rho}$ is observed at $H=50\phantom{\rule{0.3em}{0ex}}\mathrm{kOe}$ at low temperatures, which is due to a two-dimensional weak-localization effect. Below ${T}_{\mathit{cu}}$, a two-dimensional superconducting phase occurs in each TaC layer. The linear and nonlinear susceptibilities ${\ensuremath{\chi}}_{1}^{\ensuremath{''}}$, ${\ensuremath{\chi}}_{3}^{\ensuremath{'}}$, ${\ensuremath{\chi}}_{5}^{\ensuremath{'}}$, and ${\ensuremath{\chi}}_{7}^{\ensuremath{'}}$ as well as the difference $\ensuremath{\delta}\ensuremath{\chi}$ $(={\ensuremath{\chi}}_{\mathit{FC}}\ensuremath{-}{\ensuremath{\chi}}_{\mathit{ZFC}})$ between the field-cooled (FC) and zero-field-cooled (ZFC) susceptibilities start to appear below $6.0\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the onset temperature of irreversibility. A drastic growth of the in-plane superconducting coherence length below $6.0\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ gives rise to a three-dimensional superconducting phase below ${T}_{\mathit{cl}}$ through interplanar Josephson couplings between adjacent TaC layers. The oscillatory behavior of ${\ensuremath{\chi}}_{3}^{\ensuremath{''}}$, ${\ensuremath{\chi}}_{5}^{\ensuremath{''}}$, and ${\ensuremath{\chi}}_{7}^{\ensuremath{''}}$ below ${T}_{\mathit{cl}}$ is related to the nonlinear behavior arising from the thermally activated flux flow.

To investigate the origin of the enhanced $T_c$ ($\approx$ 110 K) of the trilayer cuprate superconductor Bi$_{2}$Sr$_{2}$Ca$_{2}$Cu$_{3}$O$_{10+\delta}$ (Bi-2223), we have performed systematic magnetoresistance (MR) measurements on this superconductor, as well as on the bilayer superconductor, Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ (Bi-2212). The in-plane coherence length, $\xi_{ab}$, and the specific-heat jump, ${\Delta}C$, have been estimated using the theory of renormalized superconductive fluctuations, and the doping dependence of these parameters has been qualitatively explained using the Fermi arc approach. A detailed comparison of the superconducting parameters with $T_c$ for these compounds suggests that an additional superconducting condensation energy exists, due to an increase in the number of stacking CuO$_{2}$ planes in a unit cell., Comment: 17 pages, 5 figures, to appear in JPSJ

The charge dynamics of the spin ladder compound Sr14-xCaxCu24O41 with x=0,6,13.6 has been investigated using wavelength- and temperature-dependent phonon Raman scattering on single crystals. In the unsubstituted, x=0, compound, a set of sharp two-phonon lines shows a strong increase in intensity below T similar to 200 K for light polarized along the ladder layer and with excitation energy close to the charge transfer gap similar to 1.9 eV. The temperature dependence of the strongly enhanced two-phonon bands below 200 K closely follows the recently reported formation of a standing charge density wave in the ladders [P. Abbamonte , Nature 431, 1078 (2004)]. Upon calcium substitution the polarized resonant Raman response rapidly decreases, signaling an increase of hole mobility in the ladder units. Temperature-dependent measurements of the x=13.6 sample indicate mobility of holes down to < 8 K.

A large‐size single‐crystal of the perovskite BaBiO3 has been successfully grown by the floating‐zone (FZ) method. The FZ growth was carried out under flowing O2 gas at 2 atm in an infrared heating furnace equipped with the quartet ellipsoidal mirrors. The growth rate was 1 mm/h. The rotation speed of the upper and lower shafts was 10 rpm in the opposite direction. Diffraction spots in the x‐ray back‐Laue photograph of the grown crystal were very sharp, indicating the good quality of the grown crystal. The powder x‐ray diffraction revealed that the grown crystal was of the single phase of BaBiO3.

We have measured the thermal conductivity along the b axis, κb parallel to the one‐dimensional (1D) spin chain of Sr2Cu1−xPdxO3 single crystals including nonmagnetic impurities of Pd2+, in order to investigate possible ballistic thermal conduction. It has been found that the mean free path of spinons estimated from the thermal conductivity due to spinons, which is obtained by subtracting the thermal conductivity due to phonons from κb using the Debye model, is comparable with the average length of finite spin chains between spin defects estimated from the magnetic susceptibility measurements. This proves that the thermal conduction due to spinons at low temperatures in the 1D spin system Sr2CuO3 is ballistic.

Single crystals of the perovskite Ba1 xCsxBiO3 with x = 0 22 have been successfully synthesized by the electrochemical method from molten salts. The electrodeposition of Ba1 xCsxBiO3 from CsOH H2O flux containing Ba(OH)2 8H2O and Bi2O3 was performed in a Teflon crucible under a water‐saturated argon atmosphere at 270 °C. Single crystals of high quality were grown up to 1 × 1 × 1 mm3 in size. The crystal symmetry was cubic at room temperature. However, no superconductivity was observed above 2 K in the magnetic susceptibility measurements.

The thermal conductivity in the ab plane, κab, of La2−xBaxCuO4 (x = 0.06, 0.08, 0.10, 0.11) single crystals has been measured in magnetic fields parallel to the c axis up to 14 T. By the application of magnetic field, κab has been found not to be suppressed for x = 0.06 and 0.08, while it has been found to be suppressed at low temperatures below about the superconducting transition temperature for x = 0.10 and 0.11. The suppression of κab is smaller for x = 0.11 than for x = 0.10. These results strongly support the stripe‐pinning model for the field‐induced magnetic order where the dynamically fluctuating stripes of spins and holes are regarded as being pinned by vortex cores, leading to the development of the static stripe order.

In order to investigate the possible ferromagnetic phase in the non-superconducting (non-SC) heavily overdoped (HOD) regime of high-Tc cuprates suggested by Sonier et al. [Proc. Natl. Acad. Sci. USA 107, 17131 (2010)] in La2-xSrxCuO4, both the magnetization and in-plane electrical resistivity, ρab, have been measured using single crystals of Bi1.76Pb0.35Sr1.89CuO6+δ covering a wide range of hole concentration. Magnetization curves in the non-SC HOD regime have shown a tendency to be saturated in high magnetic fields at low temperatures, which is probably a precursor of the possible ferromagnetic transition at a lower temperature. In addition, it has been found that ρab exhibits the temperature dependence being proportional to T4.3, which is characteristic of a metal with two-dimensional ferromagnetic fluctuations, in a wide range of hole concentration from the superconducting overdoped to the non-SC HOD regime. It has been concluded that two-dimensional ferromagnetic correlation develops at low temperatures in HOD Bi-2201 and that therefore the development of the ferromagnetic correlation is probably an intrinsic feature in the HOD cuprates.

Low-temperature specific heat measurements in various magnetic fields parallel and perpendicular to the c-axis for annealed single crystals of the iron-chalcogenide superconductor FeSe1-xTex have revealed that the anisotropy of the enhancement of the residual electronic- specific-heat-coefficient in the ground state by the application of magnetic field, namely, the anisotropy of the upper critical field, Hc2, is 2.2 for x = 0.6, which is different from the anisotropy of Hc2 estimated from the resistivity measurements in non-annealed single crystals of x = 0.6 [Khim et al. 2010 Phys. Rev. B 81 184511]. It appears that the anisotropy of Hc2 strongly depends on the content of excess iron included in a crystal.

We have measured the thermal conductivity in the $ab$ plane of ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ $(x=0.10,0.115,0.13)$ in magnetic fields up to $14\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ parallel to the $c$ axis and also parallel to the $ab$ plane. By the application of magnetic fields parallel to the $c$ axis, the thermal conductivity has been found to be suppressed at low temperatures below the temperature ${T}_{\ensuremath{\kappa}}$ which is located above the superconducting transition temperature and is almost independent of the magnitude of the magnetic field. The suppression is marked in $x=0.10$ and 0.13, while it is small in $x=0.115$. Furthermore, no suppression is observed in the $1%$ $\mathrm{Zn}$-substituted ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{Cu}}_{0.99}{\mathrm{Zn}}_{0.01}{\mathrm{O}}_{4}$ with $x=0.115$. Taking into account the experimental results that the temperature dependence of the relative reduction of the thermal conductivity is quite similar to the temperature dependence of the intensity of the incommensurate magnetic Bragg peak corresponding to the static stripe order and that the $\mathrm{Zn}$ substitution tends to stabilize the static order, it is concluded that the suppression of the thermal conductivity in magnetic fields is attributed to the development of the static stripe order. The present results suggest that the field-induced magnetic order in ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ originates from the pinning of the dynamical stripes of spins and holes by vortex cores.

The correlation between the crystal structure, thermoelectric power and superconductivity has been investigated in the tetragonal low-temperature (TLT) phase of La1.6 − xNd0.4SrxCuO4 with 0.10 ⩽ × ⩽ 0.25. The crystal structure has been studied by means of high-resolution powder neutron diffraction and the Rietveld analysis. It has been found that both the rhombic distortion of the CuO4 basal plane and the change of the thermoelectric power in the TLT phase are greatest at x ∼ 0.115. Therefore, the local minimum of the superconducting transition temperature at x = 0.115 is concluded to be due to the drastic change in the electronic structure in cooperation with the large rhombic distortion of the CuO4 basal plane in the TLT phase.

We have measured the thermal conductivity of a TlCuCl$_3$ single crystal in magnetic fields up to 14 T. It has been found that the temperature dependence of the thermal conductivity exhibits a sharp peak at 4 K in zero field, which is suppressed by the application of magnetic fields up to 7 T. The peak is concluded to be attributable to the enhancement of the thermal conductivity due to phonons because of the formation of a spin-gap state. In high magnetic fields above 7 T, on the other hand, another sharp peak appears around 4 K and this is enhanced with increasing magnetic field. This peak is regarded as being attributable to the enhancement of the thermal conductivity due to magnons and/or phonons because of the drastic extension of the mean free path of magnons and/or phonons in the Bose-Einstein condensed state., Comment: 4 pages, 4 figures

In order to investigate details of the superconducting (SC) gap in the iron-chalcogenide superconductors, the specific heat, C, of FeSe_1-x_Te_x_ with x=0.6-1 has been measured in magnetic fields. Using the two-gap model, it has been found that the smaller SC gap is significantly depressed by the application of magnetic field, resulting in the increase of the slope of the C/T vs T^2^ plot at low temperatures. From the specific-heat measurements at very low temperatures down to 0.4 K, it has been found that the enhancement of the residual electronic-specific-heat-coefficient in the ground state, gamma_0_, by the application of magnetic field is much smaller than that expected for superconductors with the typical s-wave or d-wave SC paring symmetry, which is in sharp contrast to the significant enhancement of gamma_0 observed in the iron-pnictide superconductors. These results are discussed in relation to the multi-band effect in the iron-based superconductors., 6 pages, 7 figures, accepted for publication in J. Phys. Soc. Jpn

We have developed new X-ray image intensifier (Flat II) system using a large-area electron multiplier for real-time fluoroscopy. This paper describes the development of prototype Flat II that has been carried out recently. The heart of new prototype is the multiplier with a smaller channel pitch (0.2 mm) located adjacent to a photo-cathode. We performed reduction of the channel pitch of multiplier, and the optimization of the geometrical arrangement- a photo-cathode, a multiplier and an output phosphor screen in order to improve the performance of Flat II. Moreover, we discuss the spatial aliasing associated with a pitch pattern of multiplier and CCD camera. Finally, physical characteristics such as modulation transfer function (MTF), etc. are discussed.

We have attempted the crystal growth by the traveling-solvent floating-zone (TSFZ) method of La_{2-x}Ba_xCuO_4 with x~1/8, where the superconductivity is strongly suppressed. Under flowing O_2-gas of a high pressure (4 bars), we have succeeded in growing single crystals of x=0.11 with 5 mm in diameter and 20 mm in length. It has been found that both in-plane and out-of-plane electrical resistivities of the single-crystal La_{2-x}Ba_xCuO_4 with x=0.11 exhibit a clear jump at ~53 K. The temperature corresponds to the structural phase transition temperature between the orthorhombic mid-temperature (OMT) and tetragonal low-temperature (TLT) phases, T_{d2}. It has also been found that both in-plane thermoelectric power and Hall coefficient drop rapidly at T_{d2} and decrease below T_{d2} with decreasing temperature. These results are quite similar to those observed in the single-crystal La_{1.6-x}Nd_{0.4}Sr_xCuO_4 with x~1/8, suggesting that the so-called static stripe order of holes and spins in the CuO_2 plane is formed below T_{d2} in La_{2-x}Ba_xCuO_4 with x~1/8 as well as in La_{1.6-x}Nd_{0.4}Sr_xCuO_4 with x~1/8., Comment: 7 pages, 8 figures, to be published in Phys. Rev. B

We have successfully synthesized a new family of Mg-intercalated superconductor Mg x M NCl ( M = Zr,Hf ) with x ⩽ 1.0 using the electrochemical technique. The values of T c ∼15 K for M = Zr and ∼25 K for M = Hf are almost independent of x even for heavily Mg-intercalated samples of Mg 0.8 ZrNCl and Mg 1.0 HfNCl . Moreover, these values are the same as those of Li x M NCl .

In order to elucidate the relationship between the pseudogap and high-T c superconductivity, the characteristic pseudogap temperature T* in Bi 2 Sr 2 CaCu 2 O 8+δ system has been systematically evaluated as a function of doping, especially focusing on its overdoped region, by measuring the out-of-plane resistivity ρ c . Overdoped samples have been prepared by annealing TSFZ-grown Bi 2 Sr 2 CaCu 2 O 8+δ single crystals under the high oxygen pressures (990 kgf/cm 2 ). At a zero field, the ρ c showed a metallic behavior down to T c (= 62 K), while under the magnetic fields of over 3 T, ρ c showed typical upturn behavior from around 65 K upon decreasing temperature. This result suggests that the pseudogap and superconductivity are different phenomena.