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The magnetic torque of (Cu,C)Ba2Ca3Cu4Oy( (Cu,C)-1234) aligned samples with various carrier concentrations has been measured under a magnetic field of 9 T at 80 K and 90 K. The carrier concentration was determined by Hall effect measurements. From angular dependent torque measurements, the anisotropy ratio γ was estimated using the 3D anisotropic London model. The γvalues decreased from 23 to 10 with an increase in the average Hall number per CuO2 plane (nH); however, these samples showed a nearly constant Tc of about 117 K. These results indicate that the anisotropy of (Cu,C)-1234 strongly reflects the doping levels of the outer planes. [ABSTRACT FROM AUTHOR]

We report the tunneling conductance on a quadruple-layered cuprate, Ba2Ca3Cu4O8(O1-xFx)2 (2x~1.4, Tc~100K) that includes inequivalent outer (OP) and inner (IP) CuO2 planes in a unit cell. Typical tunneling conductance displays the spectral dip structures as well as the superconducting gap (SCG) with clear coherence peaks. However we sometimes observe a pseudogap (PG) like structure without coherence peak at 4.2K. The magnitude of PG at 4.2K is larger than that of SCG at 4.2K and its conductance curve displays a faint structure at low energy. Therefore its origin would be different from that of small-PG observed at above Tc. In addition, we find that there are two kinds of SCGs that originate from IP and OP, and this result suggests that the superconducting property at IP is different from that at OP because of the imbalance of doped carrier between IP and OP. The observation of large PG at low temperature suggests the existence of some form of hidden ordered state at Tc and it would coexist with superconductivity. [ABSTRACT FROM AUTHOR]

We present point contact tunneling spectroscopy measured on TlBa2Ca2Cu3O10-δ (Tl1223) with three CuO2 planes in a unit cell. Our samples of Tl1223 with Tc~91K are heavily overdoped at the outer CuO2 planes (OP), but slightly underdoped at the inner CuO2 planes (IP). The tunneling conductances on Tl1223 exhibit two kinds of gaps that originate from crystallographically inequivalent IP and OP. The overall spectral shape of tunneling conductance for Tl1223 is consistent with that observed on a bilayer Bi2Sr2CaCu2O8+δ, that is, unusual peak-dip-hump (PDH) structures are observed. The origin of PDH structures is controversial, but these results, especially, the observation of PDH for trilayer Tl1223 in which interlayer effects should be quite different from that in bilayer, put severe constraints on any theoretical model for the origin of these structures. [ABSTRACT FROM AUTHOR]

Single crystals of multi-layered Ba2Ca4Cu5O10(O,F)2 superconductor(F-0245) have been grown under a high pressure of 4.5 GPa. Single crystals with in-plane length of 500μm were typically obtained and flat shiny areas with more than 1mm2 were also observed on the surface of fractured samples. Tc values for these samples were determined by electrical resistivity measurements. These values were found to change from 70 K to 85 K by change of oxygen and fluorine contents in the starting mixture. The temperature dependence of resistivity showed characteristic of under-doped cuprate superconductors. [ABSTRACT FROM AUTHOR]

We present point contact tunneling spectroscopy measured on TlBa2Ca2Cu3O10-δ (Tl1223) with three CuO2 planes in a unit cell. Our samples of Tl1223 with Tc~91K are heavily overdoped at the outer CuO2 planes (OP), but slightly underdoped at the inner CuO2 planes (IP). The tunneling conductances on Tl1223 exhibit two kinds of gaps that originate from crystallographically inequivalent IP and OP. The overall spectral shape of tunneling conductance for Tl1223 is consistent with that observed on a bilayer Bi2Sr2CaCu2O8+δ, that is, unusual peak-dip-hump (PDH) structures are observed. The origin of PDH structures is controversial, but these results, especially, the observation of PDH for trilayer Tl1223 in which interlayer effects should be quite different from that in bilayer, put severe constraints on any theoretical model for the origin of these structures. [ABSTRACT FROM AUTHOR]

μSR measurements were performed on HgBa[sub 2]Ca[sub 4]Cu[sub 5]O[sub y] (Hg-1245) samples with T[sub c] of 108 K. Rapid enhancement of muon-spin depolarization rate and losses of initial asymmetry were found in ZF-μSR time spectra below 60 K. These indicate enhancement of magnetic correlation between Cu spins. Moreover, muons precession signals were observed below 45 K, indicating that the Hg-1245 samples were in long range ordered state. These results reveal that antiferromagnetic order is developing in the Hg-1245 superconductor below T[sub c]. [ABSTRACT FROM AUTHOR]

We have synthesized an almost single phase sample of HgBa[sub 2] Ca[sub 4] Cu[sub 5] O[sub y] with T[sub c] of 108K using a high pressure and high temperature technique. The carreier concentration, N[sub H], was deduced from the Hall coefficient R[sub H] using a simple relation (N[sub H]=1/(eR[sub H])) at 300 K and the Hall number per CuO[sub 2] plane was estimated to be 0.12 for this sample. We also observed a T² dependence of the Hall angle (cotθ[sub H]). The critical current density(J[sub c]) and irreversible field (B[sub irr]) have been estimated firm measurements of magnetic hysteresis loops assuming Bean's critical state model. The B[sub irr] for this sample as a function of temperature was lower than HgBa[sub 2] Ca[sub 2] Cu[sub 3] O[sub y] (Hg-1223). This result suggests that the anisotropy in Hg-1245 is seem to be larger than that in Hg-1223 and inter-layer coupling among five CuO[sub 2] planes in Hg-1245 becomes weaker than that in Hg-1223 by adding two CuO[sub 2] planes. [ABSTRACT FROM AUTHOR]

Single phase samples with the composition of (Cu, M)Ba2 Ca3 Cu4 Oy (CuM-1234; M=C,Al,Tl,Mg,Zn) have been synthesized using high pressure technique. We have measured the pressure dependence of superconducting transition temperature (Tc ) through insitu resistivity measurements up to 8 GPa for these samples, reproducibly. These samples indicated almost the same Tc -enhancement by applied pressure, in spite of their different ambient Tc values. The enhancement values of 8-10 K at 8 GPa pressure for these samples are found to be comparable to those of Hg-system and (B,C)-system. [ABSTRACT FROM AUTHOR]

We have synthesized the single phase samples of Cux C0.1 Ba2 Ca3 Cu4 Oz (x=0.2∼0.9). Transport and magnetic measurements and iodometric titration analysis were carried out for these materials. From these results we discuss the correlation between Tc , the Hall number, copper valence and oxygen content. The effect of the substituted M ions on Tc in (CuC, M)-l234 (M=Ni,Zn,Al,TI,Mg) is also discussed. We propose a unique selective carrier-doping mechanism in (Cu,C)- and (CuC,Mg)-1234 systems. [ABSTRACT FROM AUTHOR]

The carrier distribution among the inequivalent CuO2 planes in multilayer cuprates is investigated by63 Cu Knight shift measurement with varying the carrier concentration, δ and the number of CuO2 plane in a unit cell, n. We found that 70 (60)% of total carriers are doped selectively into two outer CuO2 planes in n = 3 (4) . This indicates resultantly that the inhomogeneity of carrier distribution increases with increasing δ and n in multilayer cuprates. [ABSTRACT FROM AUTHOR]

We report that the incorporation of hydroxide ions (OH)- significantly enhances the superconducting transition temperature (Tc) in the LnFeAsO-based superconductors (Ln1111: Ln=La, Ce, and Pr). For La1111, Tc of the (OH)- incorporated sample synthesized using high-pressure technique becomes 35 K, which is higher by 7 K than the typical optimally doped La1111 superconductors. Similar enhancement in Tc is also observed for Ce1111 and Pr1111. 1H-NMR measurement have confirmed the existence of hydrogen atoms in the samples. Accompanying the (OH)- incorporation, the lattice parameters are largely contracted, down to the values which have never been attained by any other dopings/substitutions. [ABSTRACT FROM AUTHOR]

We have succeeded to prepare Tl-1223 samples with a maximum Tc above 130K at ambient pressure using a conventional sealed quartz tube method. We found that, by adequately controlling the starting composition, it is possible to control the maximum Tc from ~120K to 130K. In order to seek the key factors for a drastic increase in the Tc, we carried out the measurements of the thermoelectric power, powder X-ray diffraction and neutron diffraction for these samples. As a result, it is found that the characteristics in the Tl-1223 samples with high Tc show essentially similar to those in the Hg-1223 with the highest Tc and are different from those in the Tl-1223 samples with low Tc. The details of the synthesis conditions, the transport properties and the refinements of the crystal structure will be presented. [ABSTRACT FROM AUTHOR]