|
|
Rodriguez, D. S., E. Rodriguez, J. Luzuriaga, J. V. Waszczak, and S. W. Cheong. "Role of anisotropy in the vortex lattice of superconductors high-Q oscillator measurements in 2H-NbSe2 and La1.825Sr.075CuO4." Physica C 229, no. 1-2 (1994): 59–64.
Abstract: Measurements of the response of the flux-line lattice in NbSe2 and La1.825Sr0.075CuO4 show important differences between these two materials. In particular, we have studied the magnetic-field and angular dependence of the response of a high-Q mechanical oscillator in fields of up to 1 T. The features seen in NbSe2 seem to be well explained in terms of a change in the pinning regime, usually termed the ''peak effect'' in the critical current, using the collective-pinning model of Larkin and Ovchivnikov within Ginzburg-Landau anisotropic theory. On the other hand the behavior found in the high-T(c) material LSCO seems to fall naturally into a description which takes into account the possibility of phase transitions in the vortex lattice and the quasi-two-dimensional character of the superconductivity.
|
|
|
|
Safar, H., H. Pastoriza, J. Guimpel, F. de la Cruz, D. J. Bishop, L. F. Schneemeyer, and J. V. Waszczak. "Breakdown of the Meissner state in YBa$2$Cu$3$O7-?." In Transport properties of superconductors, edited by R. Nicolsky, 140. Progress in High Temperature Superconductivity 25. Singapore: World Scientific, 1990.
|
|
|
|
Safar, H., C. Durán, J. Guimpel, L. Civale, J. Luzuriaga, E. Rodríguez, F. de la Cruz, C. Fainstein, L. F. Schneemeyer, and J. V. Waszczak. "Logarithmic to nonlogarithmic flux creep transition and magnetic flux hardening in BiSrCaCuO superconducting ceramics." Physica C: Superconductivity 162-164, Part 1 (1989): 665–666.
Abstract: A sharp temperature and field dependent transition from a logarithmic to a non-logarithmic flux creep behavior has been found in BiSrCaCuO superconductors. The transition is not followed by any noticeable change in the magnetization. However, vibrating reed measurements show that it coincides with a strong hardening of the magnetic structure. The transition occurs at fields and temperatures well below the reversibility line. The possible relation to the recently proposed flux lattice melting is discussed.
|
|
|
|
Safar, H., C. Durán, J. Guimpel, L. Civale, J. Luzuriaga, E. Rodriguez, F. de la Cruz, C. Fainstein, L. F. Schneemeyer, and J. V. Waszczak. "Logarithmic-to-nonlogarithmic flux-creep transition and magnetic-flux hardening in Bi-Sr-Ca-Cu-O superconducting ceramics." Physical Review B 40, no. 10 (1989): 7380.
Abstract: A sharp temperature- and field-dependent transition from a logarithmic to a nonlogarithmic flux-creep behavior has been found in Bi-Sr-Ca-Cu-O superconductors. The transition is not followed by any noticeable change in the magnetization. However, vibrating-reed measurements show that it coincides with a strong hardening of the magnetic structure. The transition occurs at fields and temperatures well below the reversibility line. The possible relation to the recently proposed flux lattice melting is discussed.
|
|
|
|
Safar, H., H. Pastoriza, F. de la Cruz, D. J. Bishop, L. F. Schneemeyer, and J. V. Waszczak. "Bulk phase transition in YBa$2$Cu$3$O7-δ single crystals." Phys. Rev. B 43, no. 16 (1991): 13610–13613.
Abstract: Precise magnetization measurements of YBa$2$Cu$3$O7-δ single crystals have found evidence for a bulk phase transition a few degrees below the superconducting critical temperature. The phase transition is indicated by a sudden drop of the lower critical field , $H_C1(T)$, separating a full coherent state at low fields and temperatures, the Meissner state, from a region at higher temperatures where magnetic excitations are induced at $H=0$.
|
|
