Magnetically induced anisotropy of flux penetration into strong-pinning superconductor/ferromagnet bilayers

We studied the impact of soft ferromagnetic permalloy (Py) on the shielding currents in a strong-pinning superconductor?YBa2Cu3O7?? with Ba2Y(Nb/Ta)O-6 nano-precipitates?by means of scanning transmission x-ray microscopy. Typically and in particular when in the thin film limit, superconductor/ferromagnet (SC/FM) bilayers exhibit isotropic properties of the flux line ensemble at all temperatures. However, in elements with small aspect ratio a significant anisotropy in flux penetration is observed. We explain this effect by local in-plane fields arising from anisotropic magnetic stray fields originated by the ferromagnet. This leads to direction-dependent motion of magnetic vortices inside the SC/FM bilayer. Our results demonstrate that small variations of the magnetic properties can have huge impact on the superconductor

Multilayering BZO nanocolumns with different defect densities for YBCO high field applications

The multilayer structures of alternating superconducting YBCO films doped with different BZO nanocolumn densities were utilized. We show that using 50 nm thick layers increases J (c) in the whole angular range by maximum 40% as compared with 200 nm single layer BZO-doped or multilayers with smaller thickness. Multilayering is found to be most effective at high magnetic fields and temperatures. These results indicate that demonstrated multilayer structures are extremely attractive for various electrical power applications in the foreseeable future. The experimental outcomes are thoroughly discussed with the mechanisms of crystalline quality and flux pinning in YBCO with different BZO nanorod densities multilayers of varying thicknesses

Enhanced flux pinning in YBCO multilayer films with BCO nanodots and segmented BZO nanorods

The flux pinning properties of the high temperature superconductor YBa2Cu3O7-d (YBCO) have been conventionally improved by creating both columnar and dot-like pinning centres into the YBCO matrix. To study the effects of differently doped multilayer structures on pinning, several samples consisting of a multiple number of individually BaZrO3 (BZO) and BaCeO3 (BCO) doped YBCO layers were fabricated. In the YBCO matrix, BZO forms columnar and BCO dot-like defects. The multilayer structure improves pinning capability throughout the whole angular range, giving rise to a high critical current density, J(c). However, the BZO doped monolayer reference still has the most isotropic J(c). Even though BZO forms nanorods, in this work the samples with multiple thin layers do not exhibit a c axis peak in the angular dependence of J(c). The angular dependencies and the approximately correct magnitude of J(c) were also verified using a molecular dynamics simulation

Pair Distribution Function Analysis of ZrO2 Nanocrystals and Insights in the Formation of ZrO2-YBa2Cu3O7 Nanocomposites

The formation of superconducting nanocomposites from preformed nanocrystals is still not well understood. Here, we examine the case of ZrO2 nanocrystals in a YBa2Cu3O7-x matrix. First we analyzed the preformed ZrO2 nanocrystals via atomic pair distribution function analysis and found that the nanocrystals have a distorted tetragonal crystal structure. Second, we investigated the influence of various surface ligands attached to the ZrO2 nanocrystals on the distribution of metal ions in the pyrolyzed matrix via secondary ion mass spectroscopy technique. The choice of stabilizing ligand is crucial in order to obtain good superconducting nanocomposite films with vortex pinning. Short, carboxylate based ligands lead to poor superconducting properties due to the inhomogeneity of metal content in the pyrolyzed matrix. Counter-intuitively, a phosphonate ligand with long chains does not disturb the growth of YBa2Cu3O7-x. Even more surprisingly, bisphosphonate polymeric ligands provide good colloidal stability in solution but do not prevent coagulation in the final film, resulting in poor pinning. These results thus shed light on the various stages of the superconducting nanocomposite formation

Complete recovery of right forebrain signs from presumptive cerebrovascular origin in an eight-year-old sport horse

In this case report, an eight-year-old Warmblood gelding is described with a presumptive vascular event resulting in severe head turn and circling to the right. The horse recovered completely from the clinical signs. Pathologies that cause asymmetrical forebrain signs in horses could be excluded. Magnetic resonance imaging revealed a flow difference in the venous sinuses that was presumably caused by cerebral venous sinus thrombosis. The horse was treated with prednisolone, antibiotics, vitamin E and B1 and acetylsalicylic acid. He was represented one month after the initial clinical signs and was clinically and neurologically normal. The horse subsequently returned to his previous level of jumping