Analysis of melt-textured YBCO with nanoscale inclusions

Recently, particles with the chemical composition Y2Ba 4CuMOx where M U, Nb, Zr, etc., and sizes in the range of 50 - 200 nm have been generated within the YBCO matrix of bulk, melt-processed superconductors in order to serve as effective flux pinning sites. By means of AFM and electron backscatter diffraction (EBSD) measurements, we analyse the spatial distribution and the size distribution of these nanoparticles within the superconducting YBCO matrix

Cross-over between channeling and pinning at twin boundaries in YBa2Cu3O7 thin films

The critical current (Jc) of highly twinned YBa2Cu3O7 films has been measured as a function of temperature, magnetic field and angle. For much of the parameter space we observe a strong suppression of Jc for fields in the twin boundary (TB) directions; this is quantitatively modeled as flux-cutting-mediated vortex channeling. For certain temperatures and fields a cross-over occurs to a regime in which channeling is blocked and the TBs act as planar pinning centers so that TB pinning enhances the overall Jc. In this regime, intrinsic pinning along the TBs is comparable to that between the twins.Comment: Submitted to PR

An AC susceptometer for the characterization of large, bulk superconducting samples

The main purpose of this work was to design, develop and construct a simple, low-cost AC susceptometer to measure large, bulk superconducting samples (up to 32 mm in diameter) in the temperature range 78-120 K. The design incorporates a double heating system that enables a high heating rate (25 K/hour) while maintaining a small temperature gradient (< 0.2 K) across the sample. The apparatus can be calibrated precisely using a copper coil connected in series with the primary coil. The system has been used successfully to measure the temperature dependence of the AC magnetic properties of entire RE-Ba-Cu-O [(RE)BCO] bulk superconducting domains. A typical AC susceptibility measurement run from 78 K to 95 K takes about 2 hours, with excellent temperature resolution (temperature step ~ 4 mK) around the critical temperature, in particular.Comment: 25 pages, 7 figures. Accepted for publication in Measurement Science and Technolog

Thermobaric Effect on Melt-Textured MBa2_2Cu3_3O7−δ_{7-\delta} (M = Y, Nd)

The effect of a short (10-30 min) thermobaric action (in the 1-5 GPa pressure and 700-1300$^\circ$C temperature range) on the structure, superconductive and mechanical properties of melt-textured-MBa$_2$Cu$_3$O$_{7-\delta}$ (M=Y, Nd) or MT-MBCO have been studied. The existence has been established of pressure-temperature--time conditions (2 GPa, 800$^\circ$C for 30 min and 900-950$^\circ$C for 15 min for MT-YBCO; 5 GPa, 850-900$^\circ$C for 15 min for MT-NdBCO) the treatment under which allows superconductive properties of the materials (because of the contact with zirconia and high pressure) to be preserved or improved, mechanical characteristics increased and the materials condensed.Comment: 2 pages (tex), 2 figures (eps), to be presented at LT2

Engineering the microstructure and magnetism of La2_2CoMnO6_6 thin films by tailoring oxygen stoichiometry

We report on the magnetic and structural properties of ferromagnetic-insulating La$_2$CoMnO$_6$ thin films grown on top of (001) STO substrates by means of RF sputtering technique. Careful structural analysis, by using synchrotron X-ray diffraction, allows identifying two different crystallographic orientations that are closely related to oxygen stoichiometry and to the features (coercive fields and remanence) of the hysteresis loops. Both Curie temperature and magnetic hysteresis turn out to be dependent on the oxygen stoichiometry. In situ annealing conditions allow tailoring the oxygen content of the films, therefore controlling their microstructure and magnetic properties

Nanoscale magnetic structure and properties of solution-derived self-assembled La0.7Sr0.3MnO3 islands

The following article appeared in Journal of Applied Physics 111.2 (2012): 024307 and may be found at http://scitation.aip.org/content/aip/journal/jap/111/2/10.1063/1.3677985Strain-induced self-assembled La0.7Sr0.3MnO 3 nanoislands of lateral size 50-150 nm and height 10-40 nm have been grown on yttria-stabilized zirconia (001)-substrates from ultradiluted chemical solutions based on metal propionates. The nanoislands grow highly relaxed withstanding the epitaxial relation (001)LSMO[110]//(001) Ysz[010] and show bulk-like average magnetic properties in terms of Curie temperature and saturation magnetization. The interplay of the magnetocrystalline and shape anisotropy within the nanoisland ensemble results in an in-plane magnetic anisotropy with a magnetocrystalline constant K 1(150K) = -(5±1) kJ/m3 and in-plane easy axis along the [110] -La0.7Sr0.3MnO3 direction as measured, for the first time, through ferromagnetic resonance experiments. Magnetic force microscopy studies reveal the correlation between nanoisland size and its magnetic domain structure in agreement with micromagnetic simulations. In particular, we have established the required geometric conditions for single domain, multidomain, and vortex configurations.We acknowledge the financial support from MEC (MAT2008-01022, Consolider NANOSELECT and FPU), Comunidad Autónoma de Madrid (CAM S2009/MAT-1467), Generalitat de Catalunya (Catalan Pla de Recerca 2009-SGR- 770 and XaRMAE), and EU (NESPA). R. D. Zysler and C. A. Ramos acknowledge support from PIP-1333(2007) CONICET and PICT 829 (2006) and PICT 832(2006) ANPCyT of Argentina. Serveis Científic-Tècnics from Universitat de Barcelona and Servei de Micròscopia from Universitat Auto`noma de Barcelona are acknowledged for TEM facilities

Depth resolved lattice-charge coupling in epitaxial BiFeO3 thin film

For epitaxial films, a critical thickness (t(c)) can create a phenomenological interface between a strained bottom layer and a relaxed top layer. Here, we present an experimental report of how the t(c) in BiFeO3 thin films acts as a boundary to determine the crystalline phase, ferroelectricity, and piezoelectricity in 60 nm thick BiFeO3/SrRuO3/SrTiO3 substrate. We found larger Fe cation displacement of the relaxed layer than that of strained layer. In the time-resolved X-ray microdiffraction analyses, the piezoelectric response of the BiFeO3 film was resolved into a strained layer with an extremely low piezoelectric coefficient of 2.4 pm/V and a relaxed layer with a piezoelectric coefficient of 32 pm/V. The difference in the Fe displacements between the strained and relaxed layers is in good agreement with the differences in the piezoelectric coefficient due to the electromechanical couplingope

The Ecology of Antibiotic Use in the ICU: Homogeneous Prescribing of Cefepime but Not Tazocin Selects for Antibiotic Resistant Infection

Background: Antibiotic homogeneity is thought to drive resistance but in vivo data are lacking. In this study, we determined the impact of antibiotic homogeneity per se, and of cefepime versus antipseudomonal penicillin/beta-lactamase inhibitor combinations (APP-beta), on the likelihood of infection or colonisation with antibiotic resistant bacteria and/or two commonly resistant nosocomial pathogens (methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa). A secondary question was whether antibiotic cycling was associated with adverse outcomes including mortality, length of stay, and antibiotic resistance

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

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