Korrelation zwischen der Realstruktur und den physikalischen Eigenschaften von HTSL-Einkristallen und -Schichten Abschlussbericht

1. Mittels Phasendiagrammuntersuchungen sowie Kristallisationsexperimenten bei unterschiedlichem Sauerstoffpartialdruck wurde das primaere Kristallisationsfeld des YBCO bestimmt und die isotherme Zuechtung ermoeglicht. 2. Es wurden aus Hochtemperaturloesungen YBCO-Einkristalle hoher kristallographischer Perfektion hergestellt und Aussagen zum Verstaendnis der Flussverankerung gewonnen. 3. Mittels Fluessigphasenepitaxie (LPE) von YBCO auf NdGaO_3- und LaGaO_3-Substraten sind c- und (international erstmalig) a,b-Schichten mit Einkritallqualitaet (Tc#approx#90 K, #DELTA#T#<=#0.5 K) hergestellt und strukturell wie auch magnetisch charakterisiert worden. 4. Erste schmelztexturierte YBCO-''Einkristalle'' haben intrakristalline Stromdichten > 10"4 A/cm"2 bei Induktionen bis zu 2 T und Rreversibilitaetsinduktionen bis 6 T bei 77 K. Zusammen mit Kooperationspartnern wurden Vorstellungen zum Wachstumsmechanismus entwickelt und publiziert. 5. Insbesondere mit torsionsmagnetometrischen Untersuchungen ist es gelungen, intrinsische von realstrukturbedingten Effekten abzutrennen und damit die Moeglichkeiten einer gezielten Beeinflussung der Pinningeigenschaften abzugrenzen. 6. Die im wesentlichen eigenstaendigen Beitraege zur Theorie magnetischer Messverfahren fuehrten zur Separation von geometrischen und apparativen Einfluessen und damit zu einer klaren Interpretation magnetischer Messungen, insbesondere der Torsionsmagnetometric und der ac-Suszeptometrie. (orig./MM)1. In order to carry out isothermic crystal growth experiments of YBCO the 123 primary crystallization field was determined by means of phase diagram investigations and crystal growth experiments at different oxygen partial pressure. 2. YBCO single crystals of high crystallographic perfection were grown and conclusions on the flux pinning mechanism were drawn. 3. By means of Liquid Phase Epitaxy (LPE) single crystalline (Tc#approx#90 K; #DELTA#T#<=#0.5 K) c-and a,b- YBCO fils have been prepared on NdGaO_3 and LaGaO_3 substrates. The films were characterized structurally and magnetically. 4. Our fist melt textured YBCO ''single crystals'' possess intracrystalline critical current densities >10"4 A/cm"2 at B#<=#2T. The irreversibility inductions are #<=#6 T at 77 K. A simple demonstrator was constructed together with the IFW Dresden and a growth model was developed. 5. Using above all torque magnetometer measurements we separated intrinsic pinning effects from effects which are reasoned by the microstructure. 6. Own contributions to the theory of magnetic measuring methods resulted in the separation of geometric influences and influences of experimental arrangement, what leads to a clear interpretation of magnetic measurements carried out mainly with torque magnetometry and ac-susceptometry. (orig./MM)Available from TIB Hannover: D.Dt.F.QN1(7,27) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Glaskeramisches Verfahren zur Herstellung von Hexaferritpulvern fuer die magnetische Dichtspeicherung Abschlussbericht

Available from TIB Hannover: FR 5757+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Supraleitungs- und Tieftemperaturtechnik. Herstellung, Eigenschaften und Anwendungen kristalliner Hochtemperatur-Supraleiter Abschlussbericht

1. Melt textured YBCO bulk materials possess unique properties regarding magnetic levitation and as permanent magnets. They obtain increasing international interest. 2. The project concentrated (i) on melt textured YBCO, (ii) on the analysis of effectiveness of pinning to enlarge the critical current density, and (iii) on the preparation and characterization of liquid pahse epitaxy films. 3. All relevant methods of preparation and characterization were used. 4. The melt textured YBCO multi-domain blocks developed in the frame of the project with diameter #approx# 3 cm and thickness of #approx# 1.5 cm corresponds to the international level. Relevant results were obtained concerning the analysis of the pinning effectiveness. For the first time we were able to prepare reproducibly a(b) YBCO LPE films. 5. Melt textured YBCO blocks are applied for first cryomagnetic applications in the energy and transport technique. Atomically flat YBCO LPE films are convenient as substrates for tunnel devices. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(34,60) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

The effects of context in item-based directed forgetting: Evidence for “one-shot” context storage

The effects of context on item-based directed forgetting were assessed. Study words were presented against different background pictures and were followed by a cue to remember (R) or forget (F) the target item. The effects of incidental and intentional encoding of context on recognition of the study words were examined in Experiments 1 and 2. Recognition memory for the picture contexts was assessed in Experiments 3a and 3b. Recognition was greater for R-cued compared to F-cued targets, demonstrating an effect of directed forgetting. In contrast, no directed forgetting effect was seen for the background pictures. An effect of context-dependent recognition was seen in Experiments 1 and 2, such that the hit rate and the false-alarm rate were greater for items tested in an old compared to a novel context. An effect of context-dependent discrimination was also observed in Experiment 2 as the hit rate was greater for targets shown in their same old study context compared to a different old context. The effects of context and directed forgetting did not interact. The results are consistent with Malmberg and Shiffrin’s (Journal of Experimental Psychology: Learning, Memory, and Cognition, 31, 322–336, 2005) “one-shot” context storage hypothesis that assumes that a fixed amount of context is stored in the first 1 to 2 s of the presentation of the study item. The effects of context are independent of item-based directed forgetting because context is encoded prior to the R or F cue, and the differential processing of target information that gives rise to the directed forgetting effect occurs after the cue