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Influence of High Content of Sodium Doping in Bi(pb)2212 Superconductors
(Pleiades Publishing, 2023) Faiza, Bouaïcha; Mosbah, Mohamed-Fayçal; Özyüzer, Lütfi
Abstract: We study here, the effect of high content of sodium doping on structural and electrical properties of Bi(Pb)2212 superconductors. The X-ray analysis results showed that all the prepared samples mainly belong to the superconducting tetragonal phase Bi–(Pb)2212. SEM micrographs show that the grains are closely related and have a characteristic flat shape for the superconductor Bi (Pb) 2212. For the undoped sample, the grains are randomly distributed with an average size of 5 μm. For doped samples, the morphology changes with sodium concentration. Resistivity measurements show that all samples have a superconducting character. © 2023, Pleiades Publishing, Ltd.
Citation - WoS: 6
Citation - Scopus: 7
Thermally and Optically Tunable Sub-Terahertz Superconducting Fishnet Metamaterial
(Elsevier Ltd., 2018) Sabah, Cumali; Mulla, Batuhan; Altan, Hakan; Özyüzer, Lütfi
In this paper, a novel fishnet metamaterial structure is designed and analyzed under different material combinations and under different active controlling techniques. The results indicate that, the proposed fishnet metamaterial has a single resonance with double negativity at 0.39 THz when quartz substrate and aluminum is utilized in the design. Moreover, when the metallic parts are replaced with YBCO, the proposed design also exhibits double negativity with a stronger resonance and can be used as a switch between the double negative and single negative modes if the temperature is altered. In addition to these, when substrate (quartz) is replaced with MgO, the resonance shifts from 0.39 THz to 0.26 THz and shows double negativity. Moreover, switching properties under illumination can also be obtained when the silicon is utilized in the design (MgO-YBCO combination). According to these results, it is found that, in the case that the conductivity of silicon exceeds a certain value, the character of the resonance changes from double negative to the single negative mode.
Front-End Assembly Optimization for High-Tcrf Based Magnetic Field Imaging Systems
(IOP Publishing Ltd., 2006) Akram, Rizwan; Fardmanesh, M.; Schubert, J.; Zander, W.; Banzet, Marko; Lomparski, Dieter; Schmidt, M.; Krause, Hans J.
We have investigated the rf-SQUID and its coupling to the tank circuit configurations to achieve an optimal front-end assembly for sensitive and high spatial resolution magnetic imaging systems. The investigation on the YBCO rf-SQUID coupling to the conventional LC tank circuits revealed that the coupling from the back of the SQUID substrate enhances the SQUID signal while facilitating the front-end assembly configuration. The optimal thickness of the substrate material between the SQUID and the tank circuit is 0.4mm for LaAlO3 resulting in an increase of SQUID flux-voltage transfer function signal, Vspp, of 1.5 times, and 0.5 mm for SrTiO3 with an increase of Vspp of 1.62 times compared to that of direct face to face couplings. For the rf-coupling with co-planar resonator, CPR, it has been found that the best configuration, in which a resonator is sandwiched between the SQUID substrate and resonator substrate, provides a Vspp about 3.4 times higher than the worse case where the resonator and the SQUID are coupled back to back. It has also been observed that the noise level does not depend considerably on whether a conventional LC tank circuit or a CPR is used. Though the use of resonator leads to a limitation of the achievable spatial resolution due to its flux-focusing characteristics. This resulted in favouring the use of the conventional tank circuits when considering the desired high spatial resolution. Effect of the YBCO flip-chip magnetic shielding of the SQUIDs in the back coupling with the LC-tank circuit configuration has also been investigated, in order to reduce the SQUID effective area to increase the spatial resolution and also to study the effect of the coupling of various types of the transformers to the SQUIDs. It is revealed that there is no considerable change in the flux-voltage transfer function signal level with respect to the effective shield area, while the lowest working temperature of the SQUIDs was slightly shifted higher by a couple of degrees depending on the shield area.
Citation - WoS: 13
Citation - Scopus: 12
Mgb2 Superconducting Thin Films Sequentially Fabricated Using Dc Magnetron Sputtering and Thermionic Vacuum Arc Method
(Elsevier Ltd., 2007) Okur, Salih; Kalkancı, M.; Pat, Suat; Ekem, Naci; Akan, Tamer; Balbağ, Zafer; Musa, G.; Tanoğlu, Metin
In this work, we discuss fabrication and characterization of MgB2 thin films obtained by sequential deposition and annealing of sandwich like Mg/B/Mg thin films on glass substrates. Mg and B films were prepared using DC magnetron sputtering and thermionic vacuum arc techniques, respectively. The MgB2 thin films showed superconducting critical transition at 33 K after annealing at 650 °C.

Physics / Fizik

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