|
|
Arce, R., F. de la Cruz, and P. Esquinazi. "Superconducting penetration depth in amorphous La70Cu30." Physica B+C 108B (1981): 1253–1254.
Abstract: It is shown that weak field penetration depth measurements can be used to determine the change in the normal and superconducting behaviour of amorphous samples, when heat-treated below the crystallization temperature. The results are used to discuss the validity of BCS-Gorkov relations, when applied to these materials.
|
|
|
|
Arce, R., F. de la Cruz, and P. Esquinazi. "Superconducting penetration depth in amorphous metals." Solid State Communications 38, no. 12 (1981): 1253–1255.
Abstract: We show that temperature dependent penetration depth measurements can be used to characterize the superconductive behaviour of amorphous metals.
|
|
|
|
Durán, C., P. Esquinazi, C. Fainstein, and M. Núñez Regueiro. "Anomalies in the internal friction and sound velocity in YBa2Cu3O7-x and EuBa2Cu3O7-x superconductors." Solid State Communications 65, no. 9 (1988): 957–961.
Abstract: Internal friction Q-1 and Young Modulus sound velocity vE measurements at 1 kHz in YBa2Cu3O7?x and EuBa2Cu3O7?x polycrystalline samples reveal anomalies at the superconducting transition and at not, vert, similar37 K. The anomaly in vE at not, vert, similar90 K is accompanied by an absorption peak and is in agreement with published ultrasonic measurements, suggesting a lattice deformation at the superconducting transition.
|
|
|
|
Durán, C., P. Esquinazi, J. Luzuriaga, and E. H. Brandt. "Bc1 of high-Tc La1.8Sr0.2CuO4 and amorphous Zr70Cu30 superconductors measured by a vibrating reed." Physics Letters A 123, no. 9 (1987): 485–488.
Abstract: The lower critical field Bc1 of the high-Tc superconductor La1.8Sr0.2CuO4 (Tc=40 K, Bcless-than-or-equals, slant7.7 mT) and of amorphous Zr70Cu30 (Tc=2.6K, Bc1less-than-or-equals, slant3.8 mT) is obtained from the resonance frequency ?/2? of a vibrating reed made of these materials. At applied magnetic fields Ba<Bc1, ?(Ba)=?i(Ba) as predicted for an ideally diamagnetic reed. Above Bc1 we observe a reversible linear law ?2??2inot, vert, similarB2a?B2c1. This allows a simple definition of Bc1 even in ceramic superconductors into which flux starts to penetrate at Bamuch less-thanBc1 due to their granular structure.
|
|
|
|
Esquinazi, P., and F. de la Cruz. "Phonon thermal conductivity limited by electron scattering in amorphous Zr70Cu30." Physical Review B 27, no. 5 (1983): 3069–3072.
Abstract: The low-temperature thermal conductivity of amorphous Zr70Cu30 is investigated. The lattice thermal conductivity as limited by electrons in the superconducting state has been obtained at temperatures close to Tc. This has allowed for the first time the verification of the temperature dependence of the phonon conductivity as predicted by Bardeen, Rickayzen, and Tewordt. The analysis of the data in the normal and superconducting state shows that Matthiessen's rule can be used in amorphous metals to separate the different scattering processes.
|
|
|
|
Esquinazi, P., M. E. de la Cruz, and F. de la Cruz. "Heat treatment effects in La70Cu30 amorphous system." Physica B+C 108B, no. 1-3 (1981): 1215–1216.
Abstract: It is shown that superconductivity is a useful tool to investigate the evolution of the amorphous state, when heat treatment below the crystallization temperature.
|
|
|
|
Esquinazi, P., M. E. de la Cruz, A. Ridner, and F. de la Cruz. "Heat treatment effects in amorphous metals: Zr70Cu30 and La70Cu30." Solid State Communications 44, no. 6 (1982): 941–944.
Abstract: We measured the electrical resistivity (4–300 K), superconducting critical temperature and thermal conductivity (0.5–7 K) of the amorphous metals Zr70Cu30 and La70Cu30. Heat treatments below crystallization temperature induced changes in these properties. In particular, in the first stage of the annealing of Zr70Cu30 there are systematic changes in the thermal conductivity and the critical temperature, while the electrical resistivity remains constant. We show that there is no simple correlation between the thermal conductivity processes in the low temperature and plateau regions. We also show that the thermal conductivity of as quenched La70Cu30 is typical of amorphous metals, contrary to information previously reported.
|
|
|
|
Esquinazi, P., and C. Durán. "Magnetization and pinning measurements with the vibrating Reed on high-Tc ceramics." Physica C: Superconductivity 153-155, no. Part 3 (1988): 1499–1500.
Abstract: By means of the vibrating reed technique we have measured the lower critical field and the elastic coupling of vortices to pinning centers in La-Sr-Cu-O and Eu-Cu-O ceramics.our results indicate that the diamagnetism probed by the reed and the pinning scaling behaviour depend on the amount of oxygen in the La-based ceramic. In the Eu-based sample the lower critical field has a highly anomalous temperature dependence.
|
|
|
|
Esquinazi, P., C. Durán, C. Fainstein, and M. Núñez Regueiro. "Evidence of low-energy tunneling excitations in the high-Tc superconductor YBa2Cu3O7-x." Physical Review B 37, no. 1 (1988): 545–547.
Abstract: We have measured the internal friction Q-1 and the Young's-modulus sound velocity vE at 1 kHz for YBa2Cu3O7-x. Below 20 K the relative change in the sound velocity and the temperature dependence of the internal friction perfectly resemble the behavior obtained for Suprasil W. Below 1 K we observe a logarithmic temperature dependence for the sound velocity and between 1 and 5 K a well-defined plateau in the internal friction is obtained. We find quantitative agreement with the predictions of the standard tunneling model which is widely used to explain the low-temperature properties of amorphous materials. The implications of the existence of tunneling systems in these materials are discussed.
|
|
|
|
Esquinazi, P., B. Guillet, and H. Dussel. Caracterización parcial de la evolución estructural del sistema amorfo La70Cu30., 1984.
|
|
