Papers by Author: B. Holzapfel

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Authors: C. Cai, J. Zhang, Y. Lu, Hänisch, R. Hühne, B. Holzapfel
Abstract: By controlling pulse number of laser ablation, we prepared a series of quasi-multilayers of YBa2Cu3O7-δ/M (M=incomplete oxide layer) namely 70×(40/n) (n = 2, 5, 10 and 20, pulse number of M) which were characterised with nano-scale precipitates. While the texture properties of Y123 inside qusi-multilayer hardly change, its Tc appeared much different depending on the doping level of M. X-ray θ-2θ scanning and pole figures indicated that the different growth-controlled precipitates occured inside Y123 films. In the case of M=YSZ (Yttria Stabilized Zirconia), nanosized perovskite precipitates of BaZrO3 formed as a result of solid state reaction of YSZ with Y123, leading to Tc obviously decreasing with increasing of n. In the case of M=Y2O3, however, Tc did not decrease so much at the studied range of n due to no solid state reaction mentioned above. Magneto-transport and field angular dependence showed that the critical current density in films with lower doping content (such as n = 2) was improved in large ranges of field and temperature, suggesting tailorable enhancement and anisotropy of flux pinning force.
Authors: Paul Seidel, Frank Schmidl, Veit Grosse, Sebastian Döring, Stefan Schmidt, M. Kidszun, Sylvia Haindl, I. Mönch, Ludwig Schultz, B. Holzapfel
Abstract: Thin films of iron pnictides open the way for fundamental experiments on superconductivity in this material. Thus we started to develop tunneling and Josephson junctions with pnictide film electrodes. Different preparation methods for Josephson junctions were investigated and the first results are presented. Resistive measurements show a high superconductive transition temperature of about 20 K even for the La-1111 electrode after patterning and preparation of the tunneling window. The hybrid junctions were completed with a PbIn counter electrode and normal conducting gold layers as barriers.
Authors: Ludwig Schultz, O. Perner, Wolfgang Hässler, C. Fischer, Gunter Fuchs, B. Holzapfel, Jürgen Eckert
Authors: V.S. Sarma, B. De Boer, N. Reger, J. Eickemeyer, R. Opitz, B. Holzapfel
Authors: R. Hühne, S. Fähler, B. Holzapfel, C.G. Oertel, Ludwig Schultz, Werner Skrotzki
Authors: V. Cloet, M.C. Cordero-Cabrera, T. Mouganie, Bartek A. Glowacki, M. Falter, B. Holzapfel, J. Engell, M. Bäcker, Isabel Van Driessche
Abstract: In this present work, two buffer layers (La2Zr2O7 and CeO2) were deposited by a non-contact computer-controlled ink-jet coating technique with sol-gel precursors on highly textured Ni-5%W Rolling Assisted Biaxially Textured substrates (RABiTS). Lanthanum acetate and cerium acetylacetonate were used as precursors for the LZO and CeO2 sol respectively. After a high temperature heat treatment (heating at 900°C for LZO and at 1100°C for CeO2) under reducing atmosphere, epitaxial textured buffer layers were obtained. XRD and pole figures were used to analyse the texture of the films, the microstructure was analysed by SEM.
Authors: Zainovia Lockman, X. Qi, A. Berenov, Wilfried Goldacker, Rainer Nast, B. deBoer, B. Holzapfel, J.L. MacManus-Driscoll
Authors: R. Tamm, A. Singh, V. Neu, K. Subba Rao, Werner Skrotzki, C.G. Oertel, S. Leinert, S. Fähler, Ludwig Schultz, B. Holzapfel
Abstract: Hard magnetic Sm-Co thin films were prepared on Cr buffered MgO(001) single crystals by pulsed laser deposition. The texture of the films as well as the magnetic properties were measured for films deposited at different temperatures. Sm-Co is a system with high uniaxial magnetic anisotropy, where the c-axis is the axis of easy magnetization. Thin films of this material, with high coercivity and remanence, are of increasing interest for application in magnetic miniature devices. To explore the potential of this permanent magnetic material, a strong texture with a wellaligned c-axis is required. Analysis of several pole figures shows that mainly two types of orientations develop which grow epitaxially on Cr. For one orientation, the c-axis lies n the sample surface parallel to Cr(110). The c-axis of the second orientiation is tilted by 60° out of the surface plane.
Authors: K. Subba Rao, R. Tamm, S.C. Wimbush, G.H. Cao, C.G. Oertel, Werner Skrotzki, B. Holzapfel
Abstract: Epitaxial thin films of the superconducting borocarbide compound YNi2B2C were grown on single crystal MgO (100) substrates without and with Y2O3 buffer layer using pulsed laser deposition (PLD). In both cases YNi2B2C grows with [001] normal to the substrate. However, the in-plane texture depends on the starting condition. For samples without buffer layer, oxygen from the substrate diffuses into the film and forms an Y2O3 reaction layer at the interface. As a consequence, a deficiency of Y is generated giving rise to the formation of secondary phases. On the other hand, using an artificial Y2O3 buffer layer secondary phases are suppressed. The texture of the Y2O3 layers determines the texture of the YNi2B2C film. The superconducting properties of the borocarbide films are discussed with respect to texture and phase purity.
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