44,147 research outputs found
Strong Reduction of the Field-Dependent Microwave Surface Resistance in YBCO with BaZrO_3 Inclusions
We present measurements of the magnetic field dependent microwave surface
resistance in laser-ablated YBaCuO films on SrTiO
substrates. BaZrO crystallites were included in the films using composite
targets containing BaZrO inclusions with mean grain size smaller than 1
m. X-ray diffraction showed single epitaxial relationship between
BaZrO and YBaCuO. The effective surface resistance was
measured at 47.7 GHz for 6090 K and 00.8 T. The magnetic
field had a very different effect on pristine YBaCuO and
YBaCuO/BaZrO, while for 0 only a reduction of
in the YBaCuO/BaZrO film was observed,
consistent with dc measurements. At low enough , in moderate fields
YBaCuO/BaZrO exhibited an intrinsic thin film
resistance lower than the pure film. The results clearly indicate that
BaZrO inclusions determine a strong reduction of the field-dependent
surface resistance. From the analysis of the data in the framework of simple
models for the microwave surface impedance in the mixed state we argue that
BaZrO inclusions determine very steep pinning potentials.Comment: LaTeX, 6 pages, 4 figures, uses jpconf.cls and jpconf11.clo class
files, talk given at EUCAS 2007, submitted to J. Phys.: Conf. Serie
Análise fisiográfica das várzeas do Baixo Tocantins: uma contribuição ao manejo e desenvolvimento dos sistemas de uso da terra.
Análise fisiográfica e a evolução das várzeas do Baixo Tocantins; Fisiologia fluvial; Adequação e limitações ambientais impostas aos subsistemas.bitstream/item/63563/1/Oriental-Doc149.PD
Profiles of near-resonant population-imbalanced trapped Fermi gases
We investigate the density profiles of a partially polarized trapped Fermi
gas in the BCS-BEC crossover region using mean field theory within the local
density approximation. Within this approximation the gas is phase separated
into concentric shells. We describe how the structure of these shells depends
upon the polarization and the interaction strength. A Comparison with
experiments yields insight into the possibility of a polarized superfluid
phase.Comment: 4 pages, 5 Figures, Published versio
Solos das mesobacias hidrográficas dos igarapés São João e Cumaru, município de Marapanim e Igarapé Açu.
O conhecimento das limitações edáficas de áreas de bacias hidrográficas pode representar importante subsídio ao manejo dos solos para viabilização de diferentes sistemas de uso da terra. O objetivo deste estudo foi fazer a identificação, caracterização e o mapeamento dos solos das mesobacias hidrográficas dos igarapés São João e Cumaru, no Nordeste paraense..
Skyrmions in a Doped Antiferromagnet
Magnetization and magnetoresistance have been measured in insulating
antiferromagnetic La_{2}Cu_{0.97}Li_{0.03}O_{4} over a wide range of
temperatures, magnetic fields, and field orientations. The magnetoresistance
step associated with a weak ferromagnetic transition exhibits a striking
nonmonotonic temperature dependence, consistent with the presence of skyrmions.Comment: 4+ pages, 3 figures (some low resolution), supplementary material (3
pages); discussion expanded, references added; as publishe
Surface superconductivity in multilayered rhombohedral graphene: Supercurrent
The supercurrent for the surface superconductivity of a flat-band
multilayered rhombohedral graphene is calculated. Despite the absence of
dispersion of the excitation spectrum, the supercurrent is finite. The critical
current is proportional to the zero-temperature superconducting gap, i.e., to
the superconducting critical temperature and to the size of the flat band in
the momentum space
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