Listar Ciencias Exactas y Naturales por autor "Vieira, Valdemar das Neves"
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Anisotropic irreversibility of the Abrikosov and Josephson flux dynamics in YBa/sub 2-x/Sr/sub x/Cu/sub 3/O/sub 7-[delta]/ single crystals : Bose-glass and vortex-glass features
Vieira, Valdemar das Neves; Schaf, Jacob (2002) [Artículo de periódico]Very detailed magnetic irreversibility data for fields applied along the c axis or the ab plane of a pure and untwinned YBa₂Cu₃O₇₋₈ single crystal and Sr-doped and heavily twinned YBa₂₋xSrxCu₃O₇₋₈ (x=0.25, 0.37, and 0.5) ... -
Correlation between the magnetic irreversibility limit and the zero resistance point in different granular YBa/sub 2/Cu/sub 3/O/sub 7-σ superconductors
Dias, Fabio Teixeira; Vieira, Valdemar das Neves; Rodrigues Junior, Pedro; Obradors, Xavier; Pureur Neto, Paulo; Schaf, Jacob (2008) [Artículo de periódico]We report on magnetization and magnetoresistance measurements of single-crystal, melt-processed, and polycrystalline YBa2Cu3O7− samples with the purpose of disclosing the connection between the magnetic irreversibility ... -
Effects of Ca and Sr chemical doping on the average superconducting kinetic energy of YBa2Cu3O7-δ
Vieira, Valdemar das Neves; Mendonça, A.P.A.; Dias, Fabio Teixeira; Hneda, Marlon Luiz; Pureur Neto, Paulo; Schaf, Jacob; Mesquita, Fabiano (2015) [Artículo de periódico]In this brief communication we applied the MZFC(T) and MFCC(T) reversible dc magnetizations to get the average superconducting kinetic energy density, kS(T,B) of YBa2Cu3O7-d, Y0.95Ca0.05Ba2Cu3O7-d and YBa1.75Sr0.25Cu3O7-d ... -
Effects of Zn and Mg in Cu sites of YBa/sub 2/Cu/sub 3/O/sub 7-[delta]/ single crystals on the resistive transition, fluctuation conductivity, and magnetic irreversibilities
Vieira, Valdemar das Neves; Pureur Neto, Paulo; Schaf, Jacob (2002) [Artículo de periódico]We report on the resistive transition and fluctuation conductivity of an YBa2Cu2.97Zn0.03O7-δ single crystal and on the magnetic irreversibilities of this compound in two different oxygen states and another YBa2Cu3O7-δ ... -
Granular superconductivity ina Ca-doped YBa/sub 2/Cu/sub 3/O/sub 7-σ single crystal : role of divalent impurities and the effect of applied field on the grain coupling
Vieira, Valdemar das Neves; Riegel, Izabel Cristina; Schaf, Jacob (2007) [Artículo de periódico]We investigate the effect of the divalent Ca atoms at the trivalent Y site of YBa2Cu3O7−δ on the magnetoconductivity and magnetic irreversibility of single crystals and a polycrystalline sample. The magnetic irreversibility ... -
Irreversibility limits of the Abrikosov and Josephson flux dynamics in homogeneous and granular high-T/sub c/ superconductors
Vieira, Valdemar das Neves; Silva Filho, Job Paim da; Schaf, Jacob (2001) [Artículo de periódico]The magnetic irreversibility of a high-quality YBa₂Cu₃O₇₋₈ single crystal and of the granular superconductors YBa₁.₅Sr₀.₅Cu₃O₇₋₈ and YBa₁.₇₅Sr₀.₂₅Cu₃O₇₋₈ single crystals and the polycrystalline YBa₁.₇₅Sr₀.₂₅Cu₃O₇₋₈ sample ... -
Unconventional superconducting granularity of the Y/sub 1-x/Pr/sub x/Ba/sub 2/Cu/sub 3/O/sub 7-[delta]/ compound
Barros, Fábio Martins; Pureur Neto, Paulo; Schaf, Jacob; Fabris, Frederik Wolff; Vieira, Valdemar das Neves; Jurelo, Alcione Roberto; Cantão, Mauricio Pereira (2006) [Artículo de periódico]We report on fluctuation magnetoconductivity and magnetic irreversibility of Y1−xPrxBa2Cu3O7− single crystals and a polycrystalline sample. Although our samples are all single phase orthorhombic and the single crystals ...