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Selected Works

Carmine Vittoria

High Tc

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Full-Text Articles in Electromagnetics and Photonics

Measurement Of Kappa In High Tc Superconductors, R. Karim, H. How, C. Vittoria, A. Widom Apr 2012

Measurement Of Kappa In High Tc Superconductors, R. Karim, H. How, C. Vittoria, A. Widom

Carmine Vittoria

The experimental magnetic-field derivative of the microwave absorption signal, obtained using electron paramagnetic resonance techniques, has a line shape that depends on the Ginzburg-Landau model parameter κ of the superconducting sample at a given temperature. The type-II superconducting equation of state can be utilized to describe the drop in the output microwave power derivative, from its maximum at H ≃Hc1 to its much lower values when H ≫Hc1, in order to estimate the values of κ. The technique also allows for the experimental determination of hysteretic behavior in B as a function of H.

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Quantum Nucleation And Thermal-Activation Of Vortex Rings In High-Tc Superconductors, H. Jiang, A. Widom, Y. Huang, T. Yuan, C. Vittoria, D. B. Chrisey, J. S. Horwitz Apr 2012

Quantum Nucleation And Thermal-Activation Of Vortex Rings In High-Tc Superconductors, H. Jiang, A. Widom, Y. Huang, T. Yuan, C. Vittoria, D. B. Chrisey, J. S. Horwitz

Carmine Vittoria

Vortex-ring nucleation by thermal activation and quantum-tunneling processes in high-Tc superconductors is discussed. The nonlinear resistance scales as eν-(J/J)ν. Thermal activation yields a critical index of v = 1, while quantum tunneling (without normal current dissipation) yields a critical index of v = 2. Current-voltage characteristics were measured on both disordered (low-Jc), ordered (c axis normal to the film plane, high-Jc) Y-Ba-Cu-O films, and microbridges below Tc. The data were examined in terms of both thermal-activation and quantum-nucleation models. For the disordered films, the v = 1 scaling law is in reasonable agreement with data, while v = 2 scaling …

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