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The second harmonic signal, which is generated by co-application of AC and DC fields to polycrystalline type-II superconductors, were analyzed in terms of the weak links and the critical current density. With this aim the YBaCuZnO ( x=0, 0.01, 0.02, 0.03, 0.05, and 0.1) samples were synthesized in order to adjust intergranular couplings and thus the strength of weak links. The mechanical and magnetic measurements are in good agreement on that Zn doping reduces strength of the links between grains; however, contrary to the common expectations, it has no direct contribution to the 2nd harmonic signal strength. [ABSTRACT FROM AUTHOR]

This paper presents the synthesis and characterization of three new Y-based high temperature-superconducting compounds having relatively higher transition temperature T compared with that of the Y-123, Y-124, and Y-247. The electrical resistivity measurements indicate the onset critical temperatures as high as 98 K. Atomic compositions of these new Y-Ba-Cu-O superconductors are YBaCuO, YBaCuO, and YBaCuO. The X-ray analysis has shown that they have a similar crystalline structure as Y-123 phases. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, we investigate structural and magnetic properties of the Y8Ba5Zn4O21 structure, which was recently included in the catalog of the International Centre for Diffraction Data (ICDD) as a prototype structure. It was found that the Y8Ba5Zn4O21 bulk sample seems to be electrically insulating at temperatures of liquid nitrogen and the room temperature. On the other hand, it has quite interesting magnetic properties. Diamagnetic phase transition was observed at ~90K, which resembles that of the superconducting materials. The studied composition repels permanent magnets at the liquid nitrogen temperature. Ferromagnetism also co-exists with diamagnetism in the temperature range between 50K and 90K. Possible reasons for these behaviors are discussed. [Copyright &y& Elsevier]

Abstract: Mixing of Y2O3, BaCO3 and CuO in proper amounts to yield a net composition of YBaCu2O x reveals superconductivity above 90K without the requirement of any post-annealing under oxygen flow. Advantage of this starting composition is observed as the samples take sufficient amount of oxygen during calcination process. We found that oxygenation does not change the crystal structure and the transition temperature but it seems to be effective for improvement of the superconducting properties of intergrain regions. The J c values of as-sintered samples, which were calculated from the M–H curves, approach to the order of 106 A/cm2 at 10K. Oxygenated samples even take J c values higher than 106 A/cm2, which is mainly due to the improvement of intergrain regions. [Copyright &y& Elsevier]

Abstract: Y1Ba2Cu3O7−δ (100nm)/La0.7Sr0.3MnO3 (20nm) double-layered films and La0.7Sr0.3MnO3 (20nm) single layer films were prepared on LaAlO3 substrates by magnetron sputtering and their electrical and magnetic properties were examined. It was observed that the interactions between magnetic and superconducting layers lead to some peculiar electrical and magnetic properties such as a semiconducting-like behavior above superconducting transition temperature. Possible reasons of this behavior and others are discussed in the text. Additionally, it is observed that the SC/FM film has a quite low coercivity (50Oe) and large M r/M s ratio (0.8) at 300K. The extraordinary properties of these materials may give rise to their utilization of these films for temporary recording of information on magnetic surfaces. [Copyright &y& Elsevier]

Abstract: In the present study, we examine the energy dissipation mechanisms and grain boundary effects on the superconducting properties of high-T c SmBa2Cu3O7−x samples. Sm-123 was synthesized with the top-seeded-melt-growth technique. Grain sizes, as determined by optical microscopy, ranged between 0.5mm and 1.5mm. Thus, each specimen, on which the electrical and magnetic measurements were carried out, contained several grains. Some of our findings are as follows: (1) the intragrain T c is 93.5K and the intergrain T c is 87.5K. Superconducting transition width is narrow and is not affected much by the magnetic field. (2) The intragrain J c is 110,000Acm−2 while the intergrain J c is 210 Acm−2 at 10K. (3) The intergrain J c shows a secondary peak with the increase in temperature from 10K to 30K. The main reasons behind these observations are discussed in detail. [Copyright &y& Elsevier]

Abstract: We have synthesized bulk RuSr2RECu2O8 (RE=Eu, Gd and Ho) compounds using the ammonium nitrate melt technique. The phase purity of the samples decreases as the ionic radii of the RE element decreases. For RE=Ho, magnetic Sr2HoRuO6 and CuO were formed instead of the 1212 phase. The magnetization vs. temperature curves of the samples are similar to those of the samples prepared using the solid-state reaction method. The magnetic anomalies observed in M–T curves are discussed. [Copyright &y& Elsevier]