http://dspace-roma3.caspur.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Sat, 25 May 2013 20:31:27 GMT 2013-05-25T20:31:27Z http://dspace-roma3.caspur.it/image/logo_roma3.jpg http://dspace-roma3.caspur.it:80 http://hdl.handle.net/2307/382 <Title>Effect of BaZrO3 Inclusions on the Microwave Surface Impedance of YBCOFilms in a Magnetic Field</Title> <Authors>Pompeo, Nicola; Rogai, Raffaella; Galluzzi, Valentina; Augieri, Andrea; Celentano, Giuseppe; Ciontea, Lelia; Petrisor, Traian; Silva, Enrico</Authors> <Issue Date>2009-07-15</Issue Date> <Is part of>IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY</Is part of> <Volume>19</Volume> <Pages>2917-2920</Pages> <Abstract>We perform measurements of high-frequency (similar to 48 GHz) microwavesurface impedance with an applied magnetic field in YBa2Cu3O7-delta (YBCO) laser-ablated films with various amounts of BaZrO3 ( BZO)sub-micrometric inclusions, up to 7 mol % concentration. BZO inclusionsare very effective in the reduction of the field-induced surfaceresistance in our experimentally accessible field range [ 0, 0.8] T. Attemperatures low enough, the application of a moderate (similar to 0.2T) field makes the YBCO/BZO films markedly less dissipative than pureYBCO. This result, examined in the light of the very high measuringfrequency ( very small vortex oscillation amplitude) shows that BZOinclusions are even more effective pinning centers than columnardefects. We study the dependence of the vortex parameters ( vortexviscosity, pinning constant) on the BZO concentration. We examine thecorrelation between the reduction of the microwave dissipation and theareal density of BZO-induced defects. We argue that the very improvedperformances in a magnetic field are due to individual pinning ofvortices on BZO inclusions.</Abstract> Tue, 14 Jul 2009 22:00:00 GMT http://hdl.handle.net/2307/382 2009-07-14T22:00:00Z http://hdl.handle.net/2307/381 <Title>Transport Property Improvement by Means of BZO Inclusions in PLD GrownYBCO Thin Films</Title> <Authors>Augieri, Andrea; Galluzzi, Valentina; Celentano, Giuseppe; Angrisani, Achille Armenio; Mancini, Antonella; Rufoloni, Alessandro; Vannozzi, Angelo; Silva, Enrico; Pompeo, Nicola; Petrisor, Traian; Ciontea, Lelia; Gambardella, Umberto; Rubanov, Sergey</Authors> <Issue Date>2009-06-05</Issue Date> <Is part of>IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY</Is part of> <Volume>19</Volume> <Pages>3399-3402</Pages> <Abstract>A detailed study on YBa2Cu3O7-delta (YBCO) films with BaZrO3 (BZO)inclusions (YBCO-BZO) deposited on SrTiO3 substrate with different BZOcontents is presented. X ray diffraction, SEM imaging andsuperconductive critical temperature (T-c) measurements were performedto evaluate film growth quality. Independently from the BZO content,all YBCO-BZO films showed T-c values close to that of pure YBCOindicating that the T-c reduction which is usually observed on YBCO-BZOfilms can be successfully recovered by changing the depositionconditions. All YBCO-BZO films showed an improved critical currentdensity (J(c)) dependence on magnetic field if compared to the typicalJ(c)(H) of YBCO, resulting in higher irreversibility fields up to 9 Tat 77 K. SEM observation on etched samples suggests a direct linkbetween the defect density measured in YBCO-BZO samples and thatcalculated from the observed in field performances. The analysis ofJ(c)(B) as a function of applied magnetic field direction revealed thatthe pinning due to isotropic pinning centers typical for YBCO iscoupled with a c-axis correlated pinning in YBCO-BZO which can beascribed to BZO induced columnar defects. J(c)(B) recorded at severaltemperatures down to 10 K revealed matching effect features.</Abstract> Thu, 04 Jun 2009 22:00:00 GMT http://hdl.handle.net/2307/381 2009-06-04T22:00:00Z