Encontrados 7 documentos, a visualizar página 1 de 1
Teucrium francoi M. Seq., Capelo, J.C. Costa & R. Jardim, a new species of Teic...
Sequeira, M.M.; Capelo, J. H.; Costa, J.C.; Jardim, R.The species formerly recognized as Teucrium scorodonia in Madeira is here described as new: Teucrium francoi M. Seq., Capelo, J.C. Costa & R. Jardim. Morphologically close to species of Teucrium gr. scorodonia [T. scorodonia L., T. pseudoscorodonia Desf., T. siculum (Raf.) Guss. and T. kotschyanum Poech], it exhibits, nonetheless, some distinct diagnostic characters. The indumentum density and type of hairs of ...
Current-tuned superconductor to insulator transition in granular Sm1.82Ce0.18Cu...
Luz,M. S. da; Sandim,M. J. R.; Santos,C. A. M. dos; Machado,A. J. S.; Jardim,R. F.We have measured transport properties at low temperatures for the granular Sm1.82Ce0.18CuO4-delta samples belonging to the family of electron-doped superconductors. The effect of applied electrical current on the resistive behavior is investigated. The experimental data are analyzed using a modified form of the theory for a field-tuned superconductor-insulator transition in 2D superconductors. The results sugge...
Transport properties of granular high-T C superconductors
Luz,M. S. da; Santos,C. A. M. dos; Sandim,M. J. R.; Machado,A. J. S.; Jardim,R. F.We report on the application of the Resistively Shunted Junction (RSJ) model to granular high T C superconductors. Some derived predictions of the RSJ model are applied to a set of superconducting granular samples which can be considered as a network of Josephson junctions. The investigated samples belong to both hole-doped Y1-xPr xBa2Cu3O7-delta (x = 0.0, 0.35, and 0.45) and the electron-doped Sm2-xCe xCuO4-de...
Magnetorresistência colossal em La5/8-yPr yCa3/8MnO3
Masunaga,S. H.; Jardim,R. F.Amostras policristalinas de La5/8-yPr yCa3/8MnO3, 0 <; y <; 0,625, foram produzidas pelo método da mistura estequiométrica de óxidos e caracterizadas através de medidas resistividade elétrica ro(T, H) como função da temperatura T e do campo magnético aplicado H. Todas as amostras apresentam uma transição de fase do tipo metal-isolante T MI e aquelas com y > 0,35 também mostram uma transição para o estado de ord...
Normal-state properties of uniaxially pressed Bi1.65Pb0.35Sr2Ca2Cu3O10+delta ce...
Govea-Alcaide,E.; Muné,P.; Jardim,R. F.We have studied the effects of the uniaxial compacting pressure on the physical properties of polycrystalline Bi1.65Pb0.35Sr2Ca2Cu3O10+delta (Bi-2223) superconductors. Powders of this material were pressed at different uniaxial compacting pressures ranging from ~ 90 to ~ 600 MPa and heat-treated at the same temperature. A characterization of samples by using Scanning Electron Microscopy and X-ray diffractometry...
Superconductivity in magnetically ordered Ru1-xIr xSr2GdCu2O8 compounds
Andrade,S.; Fonseca,F. C.; Jardim,R. F.; Bossi,I.; Torikachvili,M. S.; Lacerda,A. H.; Ben-Dor,L.We have performed a systematic study of the structural, transport, and magnetic properties of polycrystalline samples of the magnetic superconductors Ru1-xIr xSr2GdCu2O8; x = 0, 0.02, 0.05, 0.10, and 0.15. The samples were prepared by solid state reaction and sintered at 1060 ºC for 72 h under O2 flow. X-ray diffraction analysis shows that all samples are nearly single phase and that the lattice parameters are ...
Preparation and general physical properties of polycrystalline PrBa2Cu3O7-y obt...
Meza,V. A.; Gratens,X.; Jardim,R. F.; Ben-Dor,L.Polycrystalline samples of PrBa2Cu3O7– y were prepared through two different routes: (a) mixing Pr6O11, BaCO3, and CuO; (b) sol-gel precursors. The samples were heat-treated in the temperature range 700 <= T <= 930 ºC and under different atmospheres, (Argon and air). Oxidation of these compounds, based on the results of thermogravimetric analysis, TGA, was performed at low temperatures, from 300 to 400 ºC, for ...
| Financiadores do RCAAP | |||||||
|
|
|
|
|
|
||