Browsing by Author "Pahlke, P."
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- ItemMagnetic granularity in pulsed laser deposited YBCO films on technical templates at 5 K(Bristol : IOP Publ., 2017-9-4) Lao, M.; Hecher, J.; Pahlke, P.; Sieger, M.; Hühne, R.; Eisterer, M.The manifestation of granularity in the superconducting properties of pulsed laser deposited YBCO films on commercially available metallic templates was investigated by scanning Hall probe microscopy at 5 K and was related to local orientation mapping of the YBCO layer. The YBCO films on stainless steel templates with a textured buffer layer of yttrium stabilized ZrO2 grown by alternating beam assisted deposition have a mean grain size of less than with a sharp texture. This results in a homogeneous trapped field profile and spatial distribution of the current density. On the other hand, YBCO films on biaxially textured NiW substrates show magnetic granularity that persists down to a temperature of 5 K and up to an applied magnetic field of 4 T. The origin of the granular field profile is directly correlated to the microstructural properties of the YBCO layer adopted from the granular NiW substrate which leads to a spatially inhomogeneous current density. Grain-to-grain in-plane tilts lead to grain boundaries that obstruct the current while out-of-plane tilts mainly affect the grain properties, resulting in areas with low . Hence, not all grain boundaries cause detrimental effects on since the orientation of individual NiW grains also contributes to observed inhomogeneity and granularity.
- ItemReversible shift in the superconducting transition for La1.85Sr0.15CuO4 and BaFe1.8Co0.2As2 using piezoelectric substrates(Milton Park : Taylor & Francis, 2010) Trommler, S.; Hühne, R.; Iida, K.; Pahlke, P.; Haindl, S.; Schultz, L.; Holzapfel, B.The use of piezoelectric substrates enables dynamic observation of the strain-dependent properties of functional materials. Based on studies with La1.85Sr0.15CuO4 (LSCO), we extended this approach to the iron arsenic superconductors represented by BaFe2− xCoxAs2 to investigate strain-driven changes in detail. We demonstrate that epitaxial thin films can be prepared on (001) Pb(Mg1/3Nb2/3)0.72Ti0.28O3 substrates using pulsed laser deposition. The structural and electric properties of grown films were characterized in detail. A reversible shift of the superconducting transition of 0.4 K for LSCO and 0.2 K for BaFe1.8Co0.2As2 was observed on applying biaxial strains of 0.022 and 0.017%, respectively.