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We have performed soft X-ray emission (SXE) and high-resolution photoemission (PE) spectroscopy to study the electronic structures of β-HfNCl and Na-intercalated HfNCl. Both the PE and SXE spectra of Na0.37HfNCl show an additional structure within the band gap of β-HfNCl, without an apparent shift in the energy position of valence-band features. These results clearly reveal intercalant-induced changes in the electronic structure of the layered nitride chlorides. From these results, we propose non-rigid band like behavior for this system in contrast to generally expected rigid-band filling upon intercalation. [Copyright &y& Elsevier]

Abstract: We have studied how the phase diagram of the Bi2Sr2−x R x CuO y system depends on the rare earth element R. The angle-resolved photoemission spectroscopy (ARPES) measurement revealed that the pseudogap is larger for the R =Eu sample than the R =La sample when compared at the same carrier concentration while the transition temperature T c of the R =La sample is larger. This implies that changing the R element to one with a smaller ionic radius stabilizes the pseudogap phase and suppresses at the same time the high-T c superconducting phase. [Copyright &y& Elsevier]

Abstract: The stability of various amounts of Ba3Cu3In4O12 (334) or BaTbO3 (BTO) in a sintered YBa2Cu3O y (YBCO) matrix was examined. Samples with added 334 or BTO exhibited critical temperatures (T c) above 90K for up to 20vol.% addition and improved critical current densities (J c) under a magnetic field. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis indicated that 334 and BTO did not react with the YBCO matrix under the sintering conditions used. The normalized J c under a magnetic field of 1T reached a maximum at 14vol.% of 334 addition and 20vol.% BTO addition. YBCO thin films with added BTO showed a gradual decrease in the T c with increasing BTO content. YBCO films with added 334 showed a constant T c of 87K up to a 334 content of 4vol.%. [Copyright &y& Elsevier]

Abstract: An effective way to improve the superconducting properties in REBa2Cu3O y (REBCO) films under a magnetic field is to dope artificial pinning centers (APC). The pinning performance depends on the content of the APC materials. Usually, the optimal APC content is explored by preparing films one at a time from the REBCO target using different APC material content, which is an extremely time-consuming process. The combinatorial-PLD (C-PLD) method allowed us to prepare films that continuously changed in composition across a single substrate. In this study, we used the C-PLD method to prepare BaSnO3 (BSO)-doped YBCO films. The films were deposited on SrTiO3 substrate using a fourth-harmonic Nd:YAG laser. From the results of the J c–B curves at 77K and B//c, the film that contained 3.2vol.% of BSO exhibited the best pinning performance in this study. We showed that the C-PLD method was efficient for quick screening of the optimal APC content with only one deposition. We also used the C-PLD method to explore new APC materials, and proved that it can quickly evaluate the new APC materials Ba3Cu3In4O12 and BaTbO3. [Copyright &y& Elsevier]

Abstract: The heavy fermion state in the f-electron systems is due to competition between the RKKY interaction and the Kondo effect. The typical compound is . To understand the electronic state, we studied the Fermi surface properties via the de Haas–van Alphen (dHvA) experiment and energy band calculation for , and nowadays, transuranium compounds. Pressure is also an important technique to control the electronic state. The Néel temperature decreases with increasing pressure P and becomes zero at the critical pressure for . The typical compound is an antiferromagnet , which we studied from the dHvA experiment under pressure. A change of the 4f-electronic state from localized to itinerant is realized at , revealing the first-order phase transition, together with a divergent tendency of the cyclotron mass at . It is stressed that appearance of superconductivity in is closely related to the heavy fermion state. It is also noted that the parity-mixed novel superconducting state might be realized in a pressure-induced superconductor without inversion symmetry in the crystal structure. [Copyright &y& Elsevier]

Abstract: We report high-resolution angle-resolved photoemission spectroscopy on single-layered cuprate superconductor (Bi,Pb)2(Sr,La)2CuO6+δ as a function of temperature and doping level, to elucidate the origin of shadow band (SB). We found that the intensity of SB is invariable with respect to temperature, doping, and substitution constituents of block layers, indicating that antiferromagnetic correlation is not responsible for the emergence of SB. Observation of similar SB in Bi2Sr2CaCu2O8+δ and La1.85Sr0.15CuO4, but not in YBa2Cu3O7−δ further supports the structural origin of SB. [Copyright &y& Elsevier]

MgB2 can be synthesized through a new route using Mg2Cu instead of pure Mg. When the temperature is elevated to around the melting point of Mg2Cu (568 °C), the Tc for Mg2Cu/B Fe-sheathed wires increases rapidly to about 37.5 K. Mg2Cu with its low melting point promotes the diffusion reaction to form a high Tc MgB2 at low temperatures. A lot of second phases forms with small amounts of MgB2 in the core of the wires. However, the transport Jc value, which is greater than 105 A/cm2 at 4.2 K in ambient fields, is rather high. Since the Jc value is estimated from a net-cross-sectional area of MgB2 it is expectedly high. Moreover, Mg2 Cu/B/metal-substrate layered composites were also prepared in this study. After a heat treatment at 600 °C for 10 h in a vacuum, a 50 μm thick MgB2 diffusion layer forms with a high-density microstructure. Cu is released from Mg2Cu, and collects on the surface of the diffusion layer. This behavior of Cu is similar to that of the bronzed process used for Nb3 Sn practical conductors. [Copyright &y& Elsevier]

MgB2 with Tc of 37 K could be fabricated through the diffusion reaction between Mg4Ag and amorphous B at relatively low temperatures above 550 °C. The melting point of Mg4Ag is 472 °C, much lower than that of pure Mg (650 °C). Therefore the reaction between Mg4Ag and B is a liquid–solid diffusion reaction. We also tried to fabricate MgB2 wires through a powder-in-tube method and an in situ reaction process by using Mg4Ag powder and amorphous B powder as the starting materials. The Jc–B properties of the wires depend on not only the size of starting powder but also the reaction temperature. [Copyright &y& Elsevier]

The voltage–current characteristics of commercial multifilamentary NbTi wires have been examined in the magnetic fields from 0 to 10 T. The measurements were performed using a specimen holder made of a fiberglass epoxy cylinder of 50 mm in diameter. The specimens of 300 mm length were spirally wound on it and the normal-state transition was measured over the central 150 mm of the specimen. The results show that in the field above 3 T the n-values determined from the V–I traces for the electric field higher than 10 μV/m increase with decreasing field, but below 2 T the n-values begin to decrease and take a minimum at about 0.5 T. [Copyright &y& Elsevier]

Abstract: We report systematic high-resolution angle-resolved photoemission results on single-layered Pb-substituted Bi2Sr2CuO6+δ . We found that the intensity of shadow bands is invariable with respect to temperature and doping. This result rules out the possibility of short-range antiferromagnetic correlation and supports the structural origin of shadow bands. [Copyright &y& Elsevier]