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- ItemPulsed laser deposition of thick BaHfO3-doped YBa 2Cu307-δ films on highly alloyed textured Ni-W tapes(Bristol : Institute of Physics Publishing, 2014) Sieger, M.; Hänisch, J.; Iida, K.; Gaitzsch, U.; Rodig, C.; Schultz, L.; Holzapfel, B.; Hühne, R.YBa2Cu3O7-δ (YBCO) films with a thickness of up to 3 μm containing nano-sized BaHfO3 (BHO) have been grown on Y2O3/Y-stabilized ZrO2/CeO 2 buffered Ni-9at% W tapes by pulsed laser deposition (PLD). Structural characterization by means of X-ray diffraction confirmed that the YBCO layer grew epitaxial. A superconducting transition temperature T c of about 89 K with a transition width of 1 K was determined, decreasing with increasing BHO content. Critical current density in self-field and at 0.3 T increased with increasing dopant level.
- ItemFemtosecond spectroscopy in a nearly optimally doped Fe-based superconductors FeSe0.5Te0.5 and Ba(Fe 1-xCox)2As2/Fe thin film(Bristol : Institute of Physics Publishing, 2014) Bonavolontà, C.; Parlato, L.; De, Lisio, C.; Valentino, M.; Pepe, G.P.; Kazumasa, I.; Kurth, F.; Bellingeri, E.; Pallecchi, I.; Putti, M.; Ferdeghini, C.; Ummarino, G.A.; Laviano, F.Femtosecond spectroscopy has been used to investigate the quasi-particle relaxation times in nearly optimally doped Fe-based superconductors FeSe 0.5Te0.5 and optimally doped Ba-122 thin films growth on a Fe buffer layer. Experimental results concerning the temperature dependence of the relaxation time of such pnictides both in the superconducting state are now presented and discussed. Modelling the T-dependence of relaxation times an estimation of both electron-phonon constant and superconducting energy gap in the excitation spectrum of both Fe(Se,Te) and Ba-122 compounds is obtained.
- ItemMeasurements of Streams Agitated by Fluid Loaded SAW-devices Using a Volumetric 3-component Measurement Technique (V3V)(Amsterdam [u.a.] : Elsevier, 2015) Kiebert, Florian; König, Jörg; Kykal, Carsten; Schmidt, HagenUtilizing surface acoustic waves (SAW) to induce tailored fluid motion via the acoustic streaming requires detailed knowledge about the acoustic bulk wave excitation. For the first time, the Defocus Digital Particle Image Velocimetry is used to measure the fluid motion originating from a fluid loaded SAW-device. With this flow measurement technique, the acoustic streaming-induced fluid motion can be observed volumetrically, which is attractive not only for application, but also for simulation in order to gain deeper insights regarding three-dimensional acoustic effects.
- ItemVisualization of Bulk Magnetic Properties by Neutron Grating Interferometry(Amsterdam [u.a.] : Elsevier, 2015) Betz, B.; Rauscher, P.; Siebert, R.; Schaefer, R.; Kaestner, A.; Van Swygenhoven, H.; Lehmann, E.; Grünzweig, C.The neutron Grating Interferometer (nGI) is a standard user instrument at the cold neutron imaging beamline ICON (Kaestner, 2011) at the neutron source SINQ at Paul Scherrer Institute (PSI), Switzerland. The setup is able to deliver simultaneously information about the attenuation, phase shift (DPC) (Pfeiffer, 2006) and scattering properties in the so-called dark-field image (DFI) (Grünzweig, 2008-I) of a sample. Since neutrons only interact with the nucleus they are often able to penetrate deeper into matter than X-rays, in particular heavier materials. A further advantage of neutrons compared to X-rays is the interaction of the neutron's magnetic moment with magnetic structures that allows for the bulk investigation of magnetic domain structures using the nGI technique (Grünzweig, 2008-II). The nGI-setup and its technique for imaging with cold neutrons is presented in this contribution. The main focus will be on magnetic investigations of electrical steel laminations using the nGI technique. Both, grain-oriented (GO) and non-oriented (NO) laminations will be presented. GO-laminations are widely used in industrial transformer applications, while NO-sheets are common in electrical machines. For grain-oriented sheet, domain walls were visualized individually,spatially resolved, while in NO-sheet a relative density distribution is depicted.
- ItemThree-Dimensional Imaging of Magnetic Domains with Neutron Grating Interferometry(Amsterdam [u.a.] : Elsevier, 2015) Manke, I.; Kardjilov, N.; Schäfer, R.; Hilger, A.; Grothausmann, R.; Strobl, M.; Dawson, M.; Grünzweig, Ch.; Tötzke, Ch.; David, Ch.; Kupsch, A.; Lange, A.; Hentschel, M.P.; Banhart, J.This paper gives a brief overview on3D imaging of magnetic domains with shearing grating neutron tomography. We investigated the three-dimensional distribution of magnetic domain walls in the bulk of a wedge-shaped FeSi single crystal. The width of the magnetic domains wasanalyzed at different locations within the crystal. Magnetic domains close to the tip of the wedge are much smaller than in the bulk. Furthermore, the three-dimensional shape of individual domains wasinvestigated. We discuss prospects and limitations of the applied measurement technique.
- ItemDetermination of Bulk Magnetic Volume Properties by Neutron Dark-Field Imaging(Amsterdam [u.a.] : Elsevier, 2015) Grünzweig, Christian; Siebert, René; Betz, Benedikt; Rauscher, Peter; Schäfer, Rudolf; Lehmann, EberhardFor the production of high-class electrical steel grades a deeper understanding of the magnetic domain interaction with induced mechanical stresses is strongly required. This holds for non-oriented (NO) as well as grain-oriented (GO) steels. In the case of non-oriented steels the magnetic property degeneration after punching or laser cutting is essential for selecting correct obstructing material grades and designing efficient electrical machines. Until now these effects stay undiscovered due to the lack of adequate investigation methods that reveal local bulk information on processed laminations. Here we show how the use of a non-destructive testing method based on a neutron grating interferometry providing the dark-field image contrast delivers spatially-resolved transmission information about the local bulk domain arrangement and domain wall density. With the help of this technique it is possible to visualize magnetization processes within the NO laminations. Different representative manufacturing techniques are compared in terms of magnetic flux density deterioration such as punching, mechanically cutting by guillotine as well as laser fusion cutting using industrial high power laser beam sources. For GO steel laminations the method is applicable on the one hand to visualize the internal domain structure without being hindered by the coating layer. On the other hand, we can show the influence of the coating layer onto the underlying domain structure.
- ItemPulsed-field Invasion to HTS Bulk Magnets Grown from Two Seeds with Varied Seed-crystal Positions and Numbers(Amsterdam [u.a.] : Elsevier, 2014) Oka, T.; Yamada, Y.; Horiuchi, T.; Ogawa, J.; Fukui, S.; Sato, T.; Yokoyama, K.; Langer, M.The flux-invasion behavior into the melt-processed Y-Ba-Cu-O bulk magnets were precisely measured and analyzed during and after their pulsed-field magnetization processes operated at 30.6 K. The materials were fabricated as the bulk monoliths grown by adopting two seed-crystals, or shifting the seed-crystal positions from the centre of the sample surface, which exhibited the magnetically single-domain distributions. Although the performances of the trapped flux density after activations showed no obvious differences, the flux started invading into the sample bearing two seeds obviously at lower fields than those of normally-grown isotropic crystal. Since the flux penetration behavior were thus clearly different between the samples with the structure grown from two seeds and uniformly grown samples with a seed crystal, it is suggested that the structure results in an effective magnetizing method with less heating than those of conventional samples, which results in the higher performance of field trapping in the bulk magnets than usual.
- ItemIn-situ investigations of structural changes during cyclic loading by high resolution reciprocal space mapping(Amsterdam : Elsevier, 2017) Diederichs, Annika M.; Thiel, Felix; Lienert, Ulrich; Pantleon, WolfgangA major failure reason for structural materials is fatigue-related damage due to repeatedly changing mechanical loads. During cyclic loading dislocations self-organize into characteristic ordered structures, which play a decisive role for the materials lifetime. These heterogeneous dislocation structures can be identified using advanced electron microscopy and synchrotron techniques. A detailed characterization of the microstructure during cyclic loading by in-situ monitoring the internal structure within individual grains with high energy x-rays can help to understand and predict the materials behavior during cyclic deformation and to improve the material design. While monitoring macroscopic stress and strain during cyclic loading, reciprocal space maps of diffraction peaks from single grains are obtained with high resolution. High Resolution Reciprocal Space Mapping was applied successfully in-situ during cyclic deformation of macroscopic aluminium samples at the Advanced Photon Source to reveal the structural reorganization within single grains embedded in the bulk material during fatigue.