Please use this identifier to cite or link to this item: http://hdl.handle.net/2307/4575
DC FieldValueLanguage
dc.contributor.advisorSilva, Enrico-
dc.contributor.authorTorokhtii, Kostiantyn-
dc.date.accessioned2015-05-27T09:39:32Z-
dc.date.available2015-05-27T09:39:32Z-
dc.date.issued2013-06-11-
dc.identifier.urihttp://hdl.handle.net/2307/4575-
dc.description.abstractThis thesis summarizes a three-year experimental study. The work is focused on the investigation of the high frequency electrical transport properties of complex superconducting systems. The experimental part included the development, setup and testing of new experimental systems, the improvement of the performance of the existing setups. First, a new dielectric resonator (DR), which operates on the TE011 mode at 8.2 GHz was designed and put into operation. Second, the existing system, based on a sapphire DR excited on the TE011 at the frequency 48 Hz was upgraded for transmission measurements. Third, the design of a rectangular DR for the study of anisotropic properties was investigated and a prototype was tested at low temperature. Two classes of complex superconducting structures were then studied: ferromagnetic/superconductor/ferromagnetic (S/F/S) Nb/Pd0.81Ni0.19/Nb multilayers, driven by the interest in the phenomena occurring due to the interaction of ferromagnetism and superconductivity, and YBa2Cu3O7-x (YBCO) samples with nanosize BaZrO3 (BZO) columnar pinning centers because of the interest in the potential applications. The investigation of Nb/PdNi/Nb and bulk Nb film samples with different PdNi layer thickness in the temperature range T=2.4-15 K and magnetic field range H=0- 3 T was performed by combining wideband (2-20 GHz) and resonant (8 GHz) measurements. The temperature dependencies of the surface resistivity and of the London penetration depth were measured, and the role of structural disorder was assessed by EXAFS spectroscopy. The evolution of the field dependence of the finite resistivity due to the free flow of magnetic flux lines was studied and compared with present theories. A previously unreported field dependence was detected and characterized for various ferromagnetic layer thickness. It was, finally, determined that for the samples with larger ferromagnetic layer, a reduction of the superfluid density induces a reduction in magnetic fields lines pinning and points to a reduction of the superfluid. YBCO/BZO samples in the temperature range T=60-120 K in magnetic field up to 0.8T were studied using resonator technique at 48 GHz. Samples prepared using different growing techniques (Pulsed laser deposition method, PLD, and Metalorganic decomposition method, MOD, were studied). The effect of the BZO concentration on flux pinning in YBCO samples was studied. The study of the field orientation revealed the flux pinning, important for the reduction of the losses was due to a dynamic (“flux caging”) effect. In summary, it was shown that microwave technique is the effective tool for the study of the microscopic properties of the various superconducting systems, which are important as for the application as for understanding of the nature of the superconductivity.it_IT
dc.language.isoenit_IT
dc.publisherUniversità degli studi Roma Treit_IT
dc.subjectsuperconductorit_IT
dc.subjectferromagnetit_IT
dc.subjectheterostructuresit_IT
dc.titleExperimental microwave properties of innovative superconductorsit_IT
dc.typeDoctoral Thesisit_IT
dc.subject.miurSettori Disciplinari MIUR::Scienze fisiche::FISICA SPERIMENTALEit_IT
dc.subject.miurScienze fisiche-
dc.subject.isicruiCategorie ISI-CRUI::Scienze fisiche::Physicsit_IT
dc.subject.isicruiScienze fisiche-
dc.subject.anagraferoma3Scienze fisicheit_IT
dc.rights.accessrightsinfo:eu-repo/semantics/openAccess-
dc.description.romatrecurrentDipartimento di Ingegneria*
item.fulltextWith Fulltext-
item.grantfulltextrestricted-
item.languageiso639-1other-
Appears in Collections:X_Dipartimento di Ingegneria
T - Tesi di dottorato
Files in This Item:
File Description SizeFormat
PhD_Thesis_Torokhtii_Kostiantyn.pdf8.3 MBAdobe PDFView/Open
Show simple item record Recommend this item

Page view(s)

69
checked on Mar 28, 2024

Download(s)

51
checked on Mar 28, 2024

Google ScholarTM

Check


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.