Polycrystalline Sr0.6K0.4Fe2As2 samples with various Pb additions (0-20 wt%) were prepared using a one-step solid state reaction. X-ray diffraction analysis shows no evidence for chemical reaction between the Pb and the FeAs-based superconductor. However, the presence of the Pb can affect the microstructure and superconducting properties of the final products. The critical transition temperature Tc indicates no degradation up to 20 wt% Pb addition, and dramatic improvements of magnetic Jc and irreversibility field Hirr were observed for appropriate Pb concentration. Transport critical current property of pure and Pb-added Sr0.6K0.4Fe2As2 tapes was also measured by a four-probe technique, and a remarkable enhancement of Jc at low fields was detected for the Pb added tapes.
Doping dependence of the upper critical field, superconducting current density and thermally activated flux flow activation energy in polycrystalline CeFeAsO1-xFx superconductors
Limits on the Superconducting Order Parameter in NdFeAsO$_{1-x}$F$_y$ from Scanning SQUID Microscopy
确定超导序参量的对称性，在最近发现的铁氧族超导体，RFeAsO $_{1-x}$ F $_{y}$，其中$R$是一种稀土，是一个高度优先事项。许多提出的序参数有内部$π$相移，如铜氧化物中发现的d波序，这将导致隧穿中的方向相关相移。在致密的多晶样品中，这些相移反过来会导致超导状态下的自发轨道电流和磁化。我们进行扫描SQUID显微镜上的致密的多晶样品的\NdFeAsO $_{0.94}$ F $_{0.06}$与$T_c=48$ K，并没有发现这样的自发电流，排除了许多建议的顺序参数。
The characteristics of the superconducting and magnetic phases in the polycrystalline samples of ruthenocuprates of nominal compositions RuSr2GdCu2O8, Ru0.98Sr2GdCu2O8 and Ru0.5Sr2GdCu2.5O8-d
本文研究了名义成分为RuSr_2GdCu_2O_8、Ru0.98Sr_2GdCu_2O_8和Ru0.5Sr_2GdCu_2.5O_8-d的超导铜氧化物的电阻率随温度的变化关系，以确定超导转变的磁场依赖特性。的Ru/Cu比在母体RuSr 2GdCu 2 O 8的显着减少的效果被证实为相关的超导相的稳定。在比较的特性中的注意到的差异被解释为可能的非均匀成核的超导相在母体xenocuprate。RuSr 2GdCu 2 O 8和Ru0.98Sr2GdCu2O8中的相各向异性，在化合物Ru磁性的存在下，似乎是Hc 2（T）相线显著软化的原因。一个异常降低的磁阻率观察到在约。10 K范围以上的超导转变的开始，这可能表明在样品中的增强的超导波动的存在。温度的正向磁场偏移限制了Ru亚晶格的磁有序态的磁阻和比热特征，这表明探测样品中存在的有效金属类导电通道中铁磁Ru相互作用的影响。的Ru0.5Sr2GdCu2.5O8-d的超导特性揭示了一个显着的贡献的Gd顺磁信号在低温下，解释为一个显着的各向异性的超导相的存在。它的结论是，Ru-Cu取代相的Cu 2 O3-Cu 2 O3
Grain Boundary Engineering Effect on Vortex Matter in Superconducting Films
Materials Genome Institute, Shanghai University（上海大学材料基因组研究院）；Department of Physics, Shanghai Normal University（上海师范大学物理系）；Department of Physics and Shanghai Key Laboratory for High Temperature Superconductors, Shanghai University（上海大学物理系及上海市高温超导重点实验室）
In this study, we determined the effect of doping with the noble metal Ag on Ir$_2$Te$_4$ superconductors. Based on the resistivity, magnetization, and heat capacity, we explored the changes in the superconductivity and charge density wave for Cu$_{1-x}$Ag$_x$Ir$_2$Te$_4$ as a function of isoelectric substitution. We assessed a complete set of competing states from suppressed charge density wave in the low doping region to superconductor in the middle doping region and re-entrant charge density wave in the high doping region, thereby obtaining an electronic phase diagram, where the superconduc…
Thermodynamic Properties of Superconducting and Non-Superconducting Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-δ}$ Compounds with Metallic Double Chains
为了研究含有金属CuO双链的Pr $_{2}$ Ba $_{4}$ Cu $_{7}$ O $_{15-δ}$化合物的热力学性质，我们测量了低温（1.8-40 K）下不同磁场（最高可达9 T）下超导和非超导多晶样品的比热。在烧结态非超导样品中，在反铁磁转变温度$T_{N}=17$ K附近出现了类似$λ-$的比热测量增强。与此相反，还原超导样品与$T_{c,on}=26.5$ K没有表现出明显的超导异常在其特定的数据，但肖特基类宽的最大值出现在低温。这种Schottky反常现象是由于Pr $^{3+}$离子在晶场作用下的低激发态准三重态分裂所致。
We study the origin of broadening of superconducting transition in sputtered Nb films. From simultaneous tunneling and transport measurements we conclude that the upper critical field Hc2 always corresponds to the bottom of transition R~0, while the top R~Rn occurs close to the critical field for destruction of surface superconductivity Hc3 ~ 1.7 Hc2. The two-dimensional nature of superconductivity at H>Hc2 is confirmed by cusp-like angular dependence of magnetoresistance. Our data indicates that surface superconductivity is remarkably robust even in disordered polycrystalline films and, surpr…
Thin films of superconducting V$_3$Si were prepared by means of RF sputtering from a compound V$_3$Si target at room temperature onto sapphire and oxide-coated silicon wafers, followed by rapid thermal processing under secondary vacuum. The superconducting properties of the films thus produced are found to improve with annealing temperature, which is ascribed to a reduction of defects in the polycrystalline layer. Critical temperatures ($T_\text{c}$) up to $15.3\,$K were demonstrated after thermal processing, compared to less than $1\,$K after deposition. The $T_\text{c}$ was found to always b…
In this work we aim to analyze the effect of a strong antisymmetric spin-orbit coupling (ASOC) on superconductivity of noncentrosymmetric LaPtSi. We study the energy gap structure of polycrystalline LaPtSi by using magnetic penetration depth measurements down to 0.02$T_c$. We observed a dirty s-wave behavior, which provides compelling evidence that the spin-singlet component of the mixed pairing state is highly dominant. This is consistent with previous results in the sense that the mere presence of a strong ASOC does not lead to unconventional behaviors. Our result also downplays LaPtSi as a …
The magnetic state of 1212-type ruthenocuprate in magnetocaloric and magnetoresistivity measurements of polycrystalline samples of RuSr2Gd1-xCexCu2O8 and Ru1-xSr2GdCu2O8
利用磁热实验和交流磁化率测量，研究了超导Ru 1-xSr 2GdCu 2 O 8（x=0，0.02）和非超导RuSr 2Gd 1-xCexCu 2 O 8（x=0.07，0.1）的磁性质.等温磁热系数M_{T}（B）在宽的温度范围内呈现正值（20 K <T<231 K）和磁场（0<B<13 T），即也处于磁有序状态（对于RuSr 2GdCu 2 O 8，T_{m} =132 K;对于RuSr2Gd0.93Ce0.07Cu2O8，T_{m} =150 K），这表明随着磁场的增加，系统的磁熵没有增加。在T_{m}附近的温度下观察到RuSr 2GdCu 2 O 8的M_{T}（B）依赖性的最大值，这表明所获得的磁关联具有铁磁特性。由于M_{T}假设在整个研究温度范围内，零磁场下的极限值为零，因此没有发现自发铁磁有序。比热的温度依赖性揭示了磁场诱导的正温度漂移的异常与磁转变的Ru自旋系统。M_{T}（B）相关性和磁阻数据表明，磁系统可能是不均匀的。
