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Herein, three issues affecting crystal growth on CdTe were resolved by the Liquinert-processed vertical Bridgman (LPVB) method, where Liquinert indicates that the “liquid is in an inert state”. The...

Phosphorus is a promising material for the electrode in sodium ion batteries (NIBs). In this study, the states of NaxPy compounds synthesized by thermochemical reaction and electrochemical sodiation were compared using solid state 23Na magic angle spinning (MAS) NMR, 23Na multiple quantum (MQ) MAS NMR, and 31P MAS NMR. The NMR signals in thermochemically synthesized NaxPy compounds (Na3P, NaP, Na3P7, Na3P11, NaP7) are assigned in reference to theoretical chemical shifts, based on first-principles calculations. Furthermore, the NMR signals in electrochemically prepared NaxPy compounds after two sodiation/desodiation cycles are ascribed to Na3P compounds and three amorphous compositions. The amorphous compounds ascribed to Na1−αP (0

Applying a radian phase shift other than 2π is a key issue for superconducting circuits, such as flux qubits. The magnetic flux is useful when generating a phase shift. However, a quantized magnetic flux accompanying a trapped vortex in a superconductor does not have a phase shifter function. The magnetic flux generated by an external field generates noise. In this study, we propose a phase bias system that does not require an external field during operation. We confirm the phase shift of a direct current superconducting interference device (SQUID) placed on an ultrathin superconducting Nb bilayer with a through-hole by cooling it to a temperature below the superconducting transition temperature with an external field. Although the cause of the phase shift in our system is unclear, we believe that it may be caused by a fractional quantum in the bilayer. When the SQUID is replaced by a qubit, the phase shift can be applied to a phase bias.

In cuprate superconductors with high critical transition temperature (Tc), light hole-doping to the parent compound, which is an antiferromagnetic Mott insulator, has been predicted to lead to the formation of small Fermi pockets. These pockets, however, have not been observed. Here, we investigate the electronic structure of the five-layered Ba2Ca4Cu5O10(F,O)2, which has inner copper oxide (CuO2) planes with extremely low disorder, and find small Fermi pockets centered at (π/2, π/2) of the Brillouin zone by angle-resolved photoemission spectroscopy and quantum oscillation measurements. The d-wave superconducting gap opens along the pocket, revealing the coexistence between superconductivity and antiferromagnetic ordering in the same CuO2 sheet. These data further indicate that superconductivity can occur without contribution from the antinodal region around (π, 0), which is shared by other competing excitations.

In cuprate superconductors with high critical transition temperature (

Calcium ferrite (CaFe 2 O 4 )-type Li x Mn 2 O 4 was prepared via high-pressure and soft chemical synthesis method. The framework structure of CaFe 2 O 4 -type NaMn 2 O 4 was synthesized from the stoichiometric mixture of Na 2 CO 3 and MnO 2 annealed by 1273 K for 1 h under 4.5 GPa. Na/Li ion-exchange of the CaFe 2 O 4 -type NaMn 2 O 4 was carried out by soaking molten LiNO 3 at 633 K for 12 h. The electrochemical properties of the ion-exchanged CaFe 2 O 4 -type Li x Mn 2 O 4 were measured. The initial discharge profile in the voltage range from 4.0 to 1.0 V showed 458 mAh g −1 of the discharge capacity with two plateaus near 3.7 V and 2.7 V (vs. Li/Li + ). The discharge capacity was decreased with increasing the cycle number. After 30 cycles, the capacity was decreased to 375 mAh g −1 . When the range was set between 4.8 and 3.0 V, the discharge capacity was 113 mAh g −1 in initial, and 111 mAh g −1 after 50th cycle. The reference CaFe 2 O 4 -type LiMn 2 O 4 was prepared via one-step high-pressure synthesis and compared the electrochemical properties with the ion-exchanged sample. The initial discharge capacity of the one-step synthesized one was 108 mAh g −1 at 1.0 V (vs. Li/Li + ), which was 73% lower than the value of the ion-exchanged one.

Scanning tunneling microscopy/spectroscopy (STM/STS) measurements were carried out on a multilayered cuprate superconductor ${\mathrm{Ba}}_{2}{\mathrm{Ca}}_{5}{\mathrm{Cu}}_{6}{\mathrm{O}}_{12}({\mathrm{O}}_{1\ensuremath{-}x},{\mathrm{F}}_{x}){}_{2}$. STM topography revealed random spot structures with the characteristic length $\ensuremath{\le}0.5$ nm. The conductance spectra $dI/dV(V)$ show the coexistence of smaller gaps ${\mathrm{\ensuremath{\Delta}}}_{S}$ and large gaps (pseudogaps) ${\mathrm{\ensuremath{\Delta}}}_{L}$. The pseudogap-related features in the superconducting state were traced with the spatial resolution of $\ensuremath{\sim}0.07$ nm. Here, $I$ and $V$ are the tunnel current and bias voltage, respectively. The temperature, $T$, dependence of ${\mathrm{\ensuremath{\Delta}}}_{S}$ follows the reduced Bardeen-Cooper-Schrieffer (BCS) dependence. The hallmark ratio $2{\mathrm{\ensuremath{\Delta}}}_{S}(T=0)/{k}_{B}{T}_{c}$ equals to 4.9, which is smaller than those of other cuprate superconductors. Here, ${T}_{c}$ is the superconducting critical temperature and ${k}_{B}$ is the Boltzmann constant. The larger gap ${\mathrm{\ensuremath{\Delta}}}_{L}$ survives in the normal state and even increases with $T$ above ${T}_{c}$. The $T$ dependencies of the spatial distributions for both relevant gaps $(\mathrm{\ensuremath{\Delta}}$ map), as well as for each gap separately $({\mathrm{\ensuremath{\Delta}}}_{S}$ and ${\mathrm{\ensuremath{\Delta}}}_{L})$, were obtained. From the histogram of $\mathrm{\ensuremath{\Delta}}$ map, the averaged gap values were found to be ${\overline{\mathrm{\ensuremath{\Delta}}}}_{S}=\ensuremath{\sim}24$ meV and ${\overline{\mathrm{\ensuremath{\Delta}}}}_{L}=\ensuremath{\sim}79$ meV. The smaller gap ${\mathrm{\ensuremath{\Delta}}}_{S}$ shows a spatially homogeneous distribution while the larger gap ${\mathrm{\ensuremath{\Delta}}}_{L}$ is quite inhomogeneous, indicating that rather homogeneous superconductivity coexists with the patchy distributed pseudogap. The spatial variation length ${\ensuremath{\xi}}_{{\mathrm{\ensuremath{\Delta}}}_{L}}$ of ${\mathrm{\ensuremath{\Delta}}}_{L}$ correlates with the scale of the topography spot structures, being approximately 0.4 nm. This value is considerably smaller than the coherence length of this class of superconductors, suggesting that ${\mathrm{\ensuremath{\Delta}}}_{L}$ is strongly affected by the disorder of the apical O/F.

Transition metal substituted CaFe 2 O 4 -type Li x (M 0.1 Mn 0.9 ) 2 O 4 (M = Ni, Ti) was synthesized by Na/Li ion exchange method from high-pressure synthesized CaFe 2 O 4 -type Na(M 0.1 Mn 0.9 ) 2 O 4 (M = Ni, Ti). The crystal structures were refined by Rietveld analysis using powder X-ray diffraction data. The electrochemical properties were measured. The initial discharge capacities of Li x (Ni 0.1 Mn 0.9 ) 2 O 4 and Li x (Ti 0.1 Mn 0.9 ) 2 O 4 were 119.3 and 122.0 mAh g −1 in the range of 4.8–3.0 V (vs Li/Li+). The capacities of substitutions were 5.29% and 7.68% increased than the value of Li 0.81 Mn 2 O 4 . After 50 charge–discharge cycles, the discharge capacities of Li 0.81 Mn 2 O 4 and Li x (Ni 0.1 Mn 0.9 ) 2 O 4 were 5.78% and 11.1% decreased from the initial. The Ni substitution was effective for increasing the discharge voltage, although the effect was decreased with increasing cycle numbers.

We report $^{63}$Cu- and $^{205}$Tl-NMR studies on six-layered ($n$=6) high-$T_c$ superconducting (SC) cuprate TlBa$_2$Ca$_5$Cu$_6$O$_{14+\delta}$ (Tl1256) with $T_c\sim$100 K, which reveal that antiferromagnetic (AFM) order takes place below $T_{\rm N}\sim$170 K. In this compound, four underdoped inner CuO$_2$ planes ($n$(IP)=4) sandwiched by two outer planes (OPs) are responsible for the onset of AFM order, whereas the nearly optimally-doped OPs responsible for the onset of bulk SC. It is pointed out that an increase in the out-of-plane magnetic interaction within an intra-unit-cell causes $T_{\rm N}\sim$ 45 K for Tl1245 with $n$(IP)=3 to increase to $\sim$170 K for Tl1256 with $n$(IP)=4. It is remarkable that the marked increase in $T_{\rm N}$ and the AFM moments for the IPs does not bring about any reduction in $T_c$, since $T_c\sim 100$ K is maintained for both compounds with nearly optimally doped OP. We highlight the fact that the SC order for $n\ge5$ is mostly dominated by the long-range in-plane SC correlation even in the multilayered structure, which is insensitive to the magnitude of $T_{\rm N}$ and the AFM moments at the IPs or the AFM interaction among the IPs. These results demonstrate a novel interplay between the SC and AFM orders when the charge imbalance between the IPs and OP is significantly large., Comment: 4 pages, 4 figures, Accepted for publication in J. Phys. Soc. Jpn

Multiband superconductors can have several types of domains that are inhibited in conventional single-band superconductors. These domains are phase domains and chiral domains and their domain wall are an interband phase difference soliton. In a superconductor with an odd number of electronic bands (five or more) and with positive interband Josephson interactions, we find other types of domains with different interband phase differences. We call these domains configuration domains because pseudo-order parameters for each band are dispersed in the complex plain and several configurations, which have several local minima. Fractional vortices serve as hubs for phase difference solitons (configuration domain walls). The divergence of the number of configurations with local minima would pose a serious problem for the stability of superconductivity.

(Cu, C)–Ba–O thin films have been deposited at low growth temperature of 450–570 °C by pulsed laser deposition method. A control of CO 2 gas pressure and the growth temperature, usage of BaCu y O x pellet target resulted in an expansion of twice c -axis length of BaCuO 2 structure (2c phase) and a significant rise of conductivity. Measurements of in-situ XPS suggest that the 2c phase should be (Cu, C)Ba 2 CuO x [(Cu, C)-1201]. The maximum temperature of onset of the superconducting transition and zero resistance state obtained so far were 60 and 47 K, respectively.

Transport properties of (Cu, C)Ba 2 CuO x [(Cu, C)-1201] thin films have been characterized by in situ temperature dependence of resistivity, without breaking vacuum from the deposition to the measurement. In in situ transport properties measurements, the obtained results reveal that (Cu, C)Ba 2 CuO x films exhibit T c > 20 K on the cased of conductivity at 290 K ( σ [290 K] ) > 4 × 10 2 S/cm and temperature coefficient of resistivity (TCR) > 1.5 × 10 −3 K −1 , and doping level of them should be in between under-doped and optimally-doped states. Their results suggest that there would be possible to further increases of T c , and XPS data suggest that (Cu, C)-system should have the excellent dopability in their charge reservoir and the possibility of low anisotropy.

By using the Hao–Clem model, we analyzed the equilibrium magnetization of the grain-aligned HgBa 2 Ca 4 Cu 5 O 12+ y (Hg1245) with T c ≃ 108 K . We obtained thermodynamic parameters, such as the penetration depth [ λ ab ( 0 ) ] and the coherence length [ ξ ab ( 0 ) ] from the thermodynamic critical field [ H c ] and the Ginzburg–Landau parameter [ κ ] . Compared to the four layered superconductor HgBa 2 Ca 3 Cu 4 O 10+ y (Hg1234), the obtained penetration depth was slightly increased indicating that the Cooper pair density of Hg1245 was decreased, which was one of the reasons why the transition temperature ( T c ) of the Hg1245 did not increase as compared to the Hg1234. The expected increase of T c for the material with the more CuO 2 planes was not achieved because of the insufficient doping of the Cooper pairs while adding CuO 2 planes.

Scanning tunneling microscopy/spectroscopy (STM/STS) measurements on multi-layered cuprate superconductor Ba2Ca5Cu6O12 (O 1-x Fx)2 are carried out. STM topographies show randomly distributed bright spot structures with a typical spot size of ~ 0.8 nm. These bright spots are occupied about 28% per one unit cell of c-plane, which is comparable to the regular amount of apical oxygen of 20% obtained from element analysis. Tunneling spectra simultaneously show both the small and the large gap structures. These gap sizes at 4.9 K are about Δ ~ 15 meV and ~ 90 meV, respectively. The small gap structure disappears at the temperature close to TC, while the large gap persists up to ~200 K. Therefore, these features correspond to the superconducting gap and pseudogap, respectively. These facts give evidence for some ordered state with large energy scale even in the superconducting state. For the superconducting gap, the ratio of 2ΔS /KBTC = 4.9 is obtained with TC = 70 K, which is determined from temperature dependence of the tunneling spectra., This research was supported by Grant-in-Aid for Scientific Research (No. 19540370) from JSPS, Japan.

We investigated that in HgBa 2 Ca n-1 Cu n O 2n+2+ δ [Hg-12( n -1) n ], for n ⩾ 6, T c of about 105 K, vortex melting lines remains constant and independent of number of inner plane CuO 2 layers. However the vortex dynamics of the supermultilayer system could be crucially different from that of single or double layer cuprates. Therefore we measured the fundamental and third harmonic AC susceptibility responses to see the vortex dynamics and vortex matter phase diagram of Hg-12( n -1) n ( n = 14), the higher member of super-multilayered cuprate superconductors. The Lindemann type vortex melting line was estimated using onset of third harmonic susceptibility ( χ 3 ), at very low h AC (50 mOe), and represented by 3D Ginzburg Landau rescaling. Frequency dependence of out of phase susceptibility χ ″(T) measured at lower fields of 500 and 1000 Oe, for 10 Hz to 10 kHz, showed resonance behaviour in the temperature region 55–68 K, suggesting rotational and translational creep dynamics of vortex molecule, even below usual melting line. We present schematic vortex phase diagram, considering the response of vortex dynamics to applied AC frequencies, taking into account the crossover temperatures obtained from critical slowing down of spin glass model and extended thermal activated model.

HgBa 2 Ca n −1 Cu n O y (Hg:12( n − 1) n ) phases have the same T c independent of n and the same vortex melting line for n ⩾ 6. In these materials, there are two types of pancake pairs: those separated by the thick block of ( n − 2) inner CuO 2 planes, which are weakly coupled by the magnetic interaction, and, respectively, those separated by the thin HgBa 2 O x charge reservoir layer, which are much stronger coupled by the Josephson coupling. The vortex melting line common to all Hg:12( n − 1) n phases ( n ⩾ 6), separates two new vortex phases, pancake-molecule-glass, and pancake-molecule-liquid.

Ba 2 Ca n −1 Cu n O 2 n (O 1− y ,F y ) 2 [F(2 y )-02( n − 1) n ], homologous series with F-substitution at apical oxygen site possess a thinner, 7.4 A, charge reservoir layer (CRL) and a strong interlayer vortex coupling was expected in these systems. We measured the vortex melting lines of high pressure synthesized Ba 2 Ca 3 Cu 4 O 8 (O 1− y F y ) 2 (2 y = 2.0) multilayered system with 2 inner planes (IP) of CuO 2 layers and Ba 2 Ca 1 Cu 2 O 4 (O 1− y F y ) 2 (2 y = 1.4, 1.6 and 2.0) bilayer system with no IP; using fundamental and third harmonic susceptibility response carried out onto preferentially oriented crystallites at very low ac field amplitude and applied dc fields up to 12 T. These experimental melting lines are described by the commonly accepted theory of two-fluid model. We observed 3D to 2D crossover in heavily underdoped F(2.0)-0212 sample, whereas such a vortex lattice crossover is not evident in F(2.0)-0234 sample; and explained on the basis of heavily underdoped and self doped states.

Change of electronic structure of superconducting (Cu, C)-1201 thin films grown by pulsed laser deposition with superconducting critical temperature Tc has been characterized by means of in situ photoemission spectroscopy. The finite spectral weight at the Fermi level in the valence band of (Cu, C)-1201 superconducting thin films and a rigid-band-like approach of the main peak of the valence band toward the Fermi level with a rise of Tc has been observed, which reveals hole-doping-induced superconductivity of this system. The obtained Ba 4d and Cu 2p signals with an increase of Tc suggest excess oxygen should be introduced around Ba ions in the early stage of the emergence of superconductivity. Then, they should be preferentially introduced around Cu ions. The changes of core signals with Tc and comparisons of the obtained data with infinite-layer and other cuprate superconductor compounds suggest that the (Cu, C)–O charge reservoir in this system is in the heavily hole-doped state, similar to that of the Cu–O chain in YBa2Cu3O7−δ.

Superconducting (Cu, C)?Ba?O thin films have been epitaxially grown on (100) SrTiO3 at a low growth temperature of 500?600??C by pulsed laser deposition. The dependences of their crystallinity and transport properties on preparation conditions have been investigated in order to clarify the dominant parameters for carbon incorporation and the emergence of superconductivity. It has been revealed that the CO3 content in the films increases with increasing both the parameters of partial pressure of CO2 during film growth and those of growth rate and enhancement of superconducting properties. The present study has also revealed that the structural and superconducting properties of the (Cu, C)?Ba?O films are seriously deteriorated by the irradiation of energetic particles during deposition. Suppression of the radiation damage is another key for a high and uniform superconducting transition. By these optimizations, a superconducting onset temperature above 50?K and a zero-resistance temperature above 40?K have been realized.

Zero- and longitudinal-field muon-spin rotation (ZF-μSR and LF-μSR) measurements were carried out on a multi-layered HgBa 2 Ca 4 Cu 5 O y (Hg-1245) superconductor with T c of 108 K. With decreasing temperature, the observed ZF-μSR function changed from a Gaussian-type to an exponential-type below 60 K and zero field muon precession was also observed below 45 K. These μSR signals are attributed to the development of the antiferromagnetic ordering in inner CuO 2 planes with a low carrier concentration. These results seem to indicate clear evidence that antiferromagnetism microscopically coexists with superconductivity in the Hg-1245 superconductor below 60 K.

We report systematic Cu-NMR studies on five-layered cuprates from under-doped HgBa2Ca4Cu5O12+δ (Hg-1245(UD)) to slightly overdoped Tl-1245(OVD), and compare with optimally-doped Hg-1245(OPT). In the under-doped Hg-1245(UD), antiferromagnetism (AFM) has been found to take place at TN = 290 K, exhibiting a large antiferromagnetic moment of 0.67–0.69 μB at three inner planes (IP’s). These values are comparable to that reported for non-doped cuprates, suggesting that the IP’s may be in a nearly non-doped regime. Most surprisingly, the AFM order is also detected with MAFM(OP) = 0.1 μB even at two outer planes (OP’s) that are responsible for the onset of superconductivity (SC) with Tc = 72 K. The high-Tc SC at Tc = 72 K can uniformly coexist on a microscopic level with the AFM at OP’s. This is the first microscopic evidence for the uniformly mixed phase of AFM and SC on a single CuO2 plane. Although, the AFM/SC mixed CuO2 planes are significantly separated by three non-doped AFM layers, the onset of AFM does not prevent the occurrence of SC with the high value of Tc = 72 K.

The magnetic torque of ( Cu , C ) Ba 2 Ca 3 Cu 4 O y ( ( 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 CuO 2 plane ( n H); 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.

We report the tunneling conductance on a quadruple-layered cuprate, Ba 2 Ca 3 Cu 4 O 8( O 1-x F x)2 (2x~1.4, Tc~100 K ) that includes inequivalent outer (OP) and inner (IP) CuO 2 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.

An AC magnetic field can rotate a vortex-molecule composed of two fractional vortices in a multiband type of multicomponent superconductor, where two components couple with each other through the intercomponent Josephson interaction. It may directly relate to an abnormal AC loss peak, which we have found recently in the multilayer cuprate supercondutor CuxBa2Ca2Cu3Oy (Cu-1223).

The multilayered cuprates of HgBa 2 Ca n −1 Cu n O y (Hg-system) and Ba 2 Ca n −1 Cu n O 2 n (O, F) (F-system) ( n = 5–9) have been synthesized under high-pressure to investigate the variation of T c . The a - and c -parameters showed reasonable behavior: as the n increases from 5 to 9 the a -parameter approached that of an infinite layer CaCuO 2 (IL) and the average interval of c (or c /2) was close to the c -parameter of the IL. All the samples showed high T c values of about 100 and 80 K for Hg- and F-system, respectively. In addition, the T c was almost constant for n ⩾ 5 for both systems. We have shown that the T c variations can be explained using inhomogeneous charge distribution model as follows. The high T c value is maintained because the charge reservoir layer supplies enough carriers for superconductivity to the adjacent CuO 2 planes (OP) even for large n . The T c is independent of n because the carrier concentration of OP is insensitive to n for large n .

It has recently been found that the T c of TlBa 2 Ca 2 Cu 3 O y (Tl-1223) is equivalent to that of Hg-1223, known as the highest T c superconductor at present. Measurements of resistivity, Hall effect, and thermoelectric power were carried out on Tl-1223 having various doping levels from high over-doping to slight over-doping. As-synthesized materials were prepared under high pressure and deoxidized by post-annealing under various conditions. The results were compared with the data for under-doped Hg-1223 reported by Fukuoka et al. The carrier concentration estimated from the thermoelectric power in both over-doped Tl-1223 and under-doped Hg-1223 showed a simple bell-shaped T c behavior. It was also observed that the Hall effect behavior of over-doped Tl-1223 resembles that of over-doped Hg-1223. These results strongly suggest that the highest T c values for the Tl and Hg systems are nearly identical at the same carrier concentration per CuO 2 plane.

Ba-Cu-O films have been grown by pulsed laser deposition. Investigation of their transport properties and characterization of electronic structure by in-situ photoemission spectroscopy have been carried out. The films grown at 450 ~ 480 °C from BaCuO2 target had simple infinite layer structure with lattice parameter of a and c about 0.385 and 0.405 nm, respectively. Conductivity of these films were, however, poor. Usage of BaCu0.75Ox target and addition of CO2 into the growth atmosphere resulted in an expansion of c-axis length up to 0.810 ~ 0.835 nm and a significant rise of conductivity. This structure is represented as ''2c''. For the 2c phase, conductivity above of 103 S/cm was achieved by adjusting their growth temperature in the range of 500 ~ 530 °C. Most of the highly conductive 2c phase showed superconductivity. The maximum temperature of onset of the superconducting transition and zero resistance state obtained so far were 60 and 47 K, respectively. Finite spectral weights at Fermi level were successfully observed in in-situ photoemission spectra of the 2c phase. In valence band region, a prominent peak with u 3d character located at a binding energy around 1.6 eV. Though this low binding energy suggested a rather high hole concentration of mobile holes were around middle of 1021 cm−3 range. These results about electronic structure indicate a coexistence of conventional CuO2 planes and distorted ones. The latter structure might play charge-reserving blocks, though some portions of holes should localize in them. Correlations between the properties and electronic structure are to be discussed.

We report the superconducting properties of (Cu, C)Ba2CuOy thin films deposited by RF magnetron sputtering from targets with a nominal composition of Ba2Cu1.5Oy. The thin films were grown in mixed Ar (5~40 mTorr), O2 (0~1.2 mTorr) and CO2 (0~1.8 mTorr) atmosphere. The epitaxial c-axis oriented thin films with c-axis length in the range between 7.96 A and 8.82 A were obtained on SrTiO3(100) substrates, but superconductivity was observed only for the films which have the c-axis length with 8.01 A and 8.32 A. By optimizing deposition conditions, the excellent (Cu, C)Ba2CuOy thin film with Tc = 62K and superconducting transition width ΔTc = 1.5 K was successfully obtained.

必要試料量がnlレベルであるキャピラリー電気泳動法により，高温酸化物超伝導体中のTlの価数分析法を開発した．四ホウ酸ナトリウム十水和物を泳動液に用い，アコイオン自体に紫外吸収を示すTl(I) はTl＋として印加電圧25.0 kVで泳動させ，波長215 nmでUV法により直接検出した．塩酸に溶解させているTl(III) はTlCl63－として印加電圧－30.0 kVで泳動させ，波長242 nmで直接検出した．共存イオンはイミダゾールを用い，間接紫外吸光法により定量した．実試料は，Tl系高温酸化物超伝導体0.20 mgを0.01 MのHClに溶解させて用いた．測定した2種類の試料はともに97％ がTl(III) という結果になった．本法を用いることで従来の方法よりも必要とする試料量を約20分の1に下げることができた．

We present point contact tunneling spectroscopy measured on TlBa 2 Ca 2 Cu 3 O 10-δ ( Tl 1223) with three CuO 2 planes in a unit cell. Our samples of Tl 1223 with Tc~91 K are heavily overdoped at the outer CuO 2 planes (OP), but slightly underdoped at the inner CuO 2 planes (IP). The tunneling conductances on Tl 1223 exhibit two kinds of gaps that originate from crystallographically inequivalent IP and OP. The overall spectral shape of tunneling conductance for Tl 1223 is consistent with that observed on a bilayer Bi 2 Sr 2 CaCu 2 O 8+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 Tl 1223 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.

Single crystals of multi-layered Ba 2 Ca 4 Cu 5 O 10( 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 1 mm 2 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.

Electrical resistivity, magnetoresistance, and specific heat measurements have been performed for the binary icosahedral Cd 5.7 Yb and its cubic approximant Cd 6 Yb. The resistivity of both the icosahedral phase (i-phase) and the approximant is found to show a rather metallic behavior with a large positive temperature coefficient of the resistivity (TCR) below 200–300 K followed by leveling-off at low temperatures below 10 K. For the approximant, we observe a stepwise change of the resistivity at 110 K which is due to a phase transition. Giant magnetoresistance as high as 200% at 9 T below 4.2 K is observed for the i-phase and the electronic specific heat coefficient γ is found to be extraordinary large in both alloys, i.e., 2.87 mJ/(mole K 2 ) for the i-phase and 7.60 mJ/(mole K 2 ) for the approximant. Such large γ values may be attributed to the Yb-derived states at the Fermi level. Furthermore, the Debye temperatures ( Θ D ) are very low and almost the same for both alloys, i.e., 142 and 144 K, respectively, which are indeed the lowest values ever reported in i-phases and approximants. The metallic character of the binary i-phase implies that the negative TCR is not necessarily a consequence of the quasiperiodicity.

A layered cuprate film, (Cu,C)Ba2Can−1CunOx (n=1; (Cu,C)-1201), consisting of the charge reservoir block and the infinite layer was prepared by sputtering BaCu0.75Ox target on a (1 0 0) SrTiO3 substrate. The effects of the substrate temperature (Ts) and CO2 concentration (Cco2) in the discharge gas on the crystallinity of the films were systematically examined. The (Cu,C)-1201 film oriented along c-axis formed on the (1 0 0) SrTiO3 substrate. The φ-scan X-ray measurement of the films showed four-fold symmetry. The Cco2 and Ts strongly affected the crystallinity of the (Cu,C)-1201 film. The deposition conditions for a (Cu,C)-1201 film with a single-crystalline phase were as follows: discharge gas, Ar+CO2 (C co 2 =2–8 vol %); Ts 520–560°C and gas pressure, 1.33 Pa. Oxygen annealing of the (Cu,C)-1201 films in a sputtering chamber at near 15 Pa during the cooling process down to 100°C generated uncompensated electrical charges (holes), resulting in low resistivity. Metallic conduction down to 50 K was observed for a film deposited in Ar+CO2 gas (C co 2 =3 vol %); at a Ts of 530°C.

Comparisons of the electrical resistivity and the electronic contribution to the specific heat have been made among the P-type icosahedral Zn81Mg6Sc13, and their crystalline approximants 2/1-Zn82Mg5Sc13 and 1/1-Zn85Sc15. The temperature dependence of the resistivity, ρ(T), is nearly the same for the quasicrystal and the 2/1-cubic approximant, with a negative coefficient and similar resistivity values, i.e., ρ(4.2 K )=350 and 300 μΩ cm, respectively. On the other hand, ρ(T) shows a metallic character with a positive coefficient and a rather low resistivity value of ρ(4.2 K )=150 μΩ cm for the 1/1-cubic approximant. Electronic specific heat coefficients, γ, are small as in other i-phases and approximants; 0.50, 0.42 and 0.71 mJ/(mol K2) for the quasicrystal, the 2/1- and the 1/1-approximants, respectively. The present result suggests that the electronic transport is essentially determined by the length scale of 22 A in the P-type i-phase.

Single crystals of multi-layered superconductors of Ba2Can−1CunO2n(O,F)2 (F-02(n − 1)n, n = 3 and 4) have been grown under a pressure of 4.5 GPa. Crystals were obtained by cooling samples with nominal compositions of Ba2Can−1CunO2nF2 (n = 2, 2.5, 3 and 4) across the melting point. The crystals are thin plate-like shapes with typical sizes of 500 µm in plane length and 30 µm in thickness. The crystals are found to show cleavage, which will be convenient for surface sensitive measurements. The F-0223 and F-0234 crystals showed Tc of 90 K and 70 K, respectively after oxygen annealing. The temperature dependence of resistivity showed pronounced underdoped behaviour. Composition analysis showed that a ratio of Ba:Ca:Cu is close to the stoichiometric composition one. We think that the F-system is a rare multi-layered cuprate that can largely grow under high pressure and its crystals are quite valuable to study both high-Tc superconductivity and the multi-layered system.

We controlled the dynamics of the superconducting order parameter keeping the same T c on Cu x Ba 2 Ca 3 Cu 4 O y . There are two pair-breaking bands corresponding to two superconducting gaps in Raman spectrum of the as-synthesized sample. One of them smeared out by a simple annealing.

Polycrystalline samples of Ba 2 Ca 3 Cu 4 O 8 (O 1-y F y ) 2 (0234F) with a variety of T c (55-105 K) were synthesized under high pressure. The dynamic range of the T c 50 K in an underdoped region, has been found to be remarkably wide. We also found that plate-like single crystals of 0234F (∼1 mm 2 in plane area and 30 μm in thickness) grow when samples with a nominal composition of y ∼ 1.0 are heated at high temperature (∼1150 °C). Cleavage was observed for the crystals. The 0234F will be a convenient material for investigations of physics of the multi-layered superconductors and/ or the underdoped state that has a key for understanding high-T c superconductivity.

Point contact tunneling data are reported in a multilayered high-T c cuprate (Cu,C)Ba 2 Ca 3 Cu 4 O 12+δ with T c = 117 K . The tunneling spectra in the superconducting state (T ≪ T c ) display spectral features such as well-defined superconducting gap peak at ±Δ as well as dip-hump structures beyond the peaks. In some cases, the spectra with two-gaps have been observed, indicating the coexistence of two inequivalent superconducting layers. The statistical distribution of superconducting gap magnitude suggests two distinct kinds of superconducting gaps that may originate from two inequivalent CuO 2 planes, a characteristics of multilayered cuprates with n ≥ 3.

μSR measurements were performed on HgBa 2 Ca 4 Cu 5 O y (Hg-1245) samples with Tc 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 Tc.

Variation of Tc in the over doped region have been investigated for Zn and Ni doped samples of TlBa2Ca2Cu3O9−δ to obtain a clue to understand the anomalous suppression of Tc. We expected that if the anomaly in Tl-1223 originates from the stripe order like La-214 system, the suppression of Tc is enhanced by the doping. The results showed that the anomaly disappeared by both of the doping contrary to the expectation so that the possibility of the stripe order was ruled out. Two possible explanations were proposed based on a self-doping mechanism and inhomogeneous charge distribution to crystallography different CuO2 layers.

We have synthesized an almost single phase sample of HgBa2Ca4Cu5O y with T c of 108K using a high pressure and high temperature technique. The carreier concentration, N H, was deduced from the Hall coefficient R H using a simple relation (N H=1/(eR H)) at 300 K and the Hall number per CuO2 plane was estimated to be 0.12 for this sample. We also observed a T 2 dependence of the Hall angle (cot θH). The critical current density (J c) and irreversible field (Birr) have been estimated from measurements of magnetic hysteresis loops assuming Bean's critical state model. The Birr for this sample as a function of temperature was lower than HgBa2Ca2Cu3O 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 CuO2 planes in Hg-1245 becomes weaker than that in Hg-1223 by adding two CuO2 planes.