Fainstein, A., P. Etchegoin, and J. Guimpel. "Raman study of photoinduced chain-fragment ordering in GdBa2Cu3Ox thin films." PHYSICAL REVIEW B 58, no. 14 (1998): 9433–9439.
Abstract: Raman scattering experiments on oxygen deficient GdBa2Cu3Ox thin films (x=6.53, 6.7, 6.8, and 6.93) as a function of photoexcitation and annealing induced oxygen disorder are presented. Raman lines, unambiguously assigned to copper and oxygen vibrations involving atoms at the end of Cu-O chains, are used as markers for the existence of short chain fragments. The dynamics of chain conjunction and fragmentation was monitored by the peak intensity dependences with photoexcitation time and annealing temperature. These results demonstrate the presence of photoassisted oxygen ordering in these high-T-c superconductors, and give definitive support for its ultimate role in the phenomena of persistent photoconductivity and photoinduced superconductivity. [S0163-1829(98)04037-5].
|
Guimpel, J., B. Maiorov, E. Osquiguil, G. Nieva, and F. Pardo. "Interrelation between persistent photoconductivity and oxygen order in GdBa2Cu3Ox thin films." Physical Review B – Condensed Matter and Materials Physics 56, no. 7 (1997): 3552–3555.
Abstract: We study the metastable states induced by photoexcitation, oxygen disorder, and both effects combined in superconducting GdBa2Cu3Ox thin films. The states are identified by the temperature dependence of the resistivity. The relaxation dynamics is characterized through the time evolution of the conductivity. The results show that photoexcitation and oxygen disorder behave as noninteracting and do not cancel each other out. However, in both cases the relaxation dynamics is related to oxygen movement .
|
Pardo, F., A. P. Mackenzie, F. delaCruz, and J. Guimpel. "Effect of the reversibility region on the low-temperature vortex structure imaged by Bitter magnetic decoration." PHYSICAL REVIEW B 55, no. 21 (1997): 14610–14613.
Abstract: We have combined magnetic measurements and imaging of the vortex lattice at low fields in Tl2Ba2CuO6-delta single crystals with different oxygen content. Those with high critical temperature T-c > 80 K have a reversible region while those with low T-c < 30 K have an irreversible magnetization in the whole range of temperatures, up to T-c. The presence of the reversible region allows the formation of ordered vortex structures, while amorphous structures are obtained when no reversible region is present below T-c. The results are discussed in terms of vortex nucleation processes in the individual pinning regime.
|
Arce, R., L. Civale, J. Luzuriaga, J. Guimpel, and F. de la Cruz. "Surface normal regions in superconducting Zr70Cu30 induced by thermal relaxation." Solid State Communications 48, no. 12 (1983): 1027–1030.
Abstract: Penetration depth measurements show that thermal heat treatment in amorphous Zr70Cu30 induces a normal region 5000 Å thick at the surface of ultrarapid quenched ribbons. Upper critical field measurements indicate that the new induced phase is a normal one while the rest of the sample remains as a homogeneous superconducting phase.
|
Arce, R., F. de la Cruz, and J. Guimpel. "Superconducting behavior of amorphous Zr70Cu30." Solid State Communications 47, no. 11 (1983): 885–887.
Abstract: Measurement of the Meissner penetration depth, λ(T) were made in amorphous Zr70Cu30 samples. The results indicate that this amorphous alloy behaves as a BCS superconductor with 2Δ(0)+45 degree rulekTc = 3.8, where Δ(0) is the superconducting energy gap at T=0 and Tc the critical temperature. It is also concluded that the low energy excitation, TLS, characteristics of amorphous material does not contribute to Tc.
|
Nieva, G., E. Osquiguil, J. Guimpel, M. Maenhoudt, B. Wuyts, Y. Bruynseraede, M. B. Maple, and I. K. Schuller. "Photoinduced changes in the transport properties of oxygen-deficient YBa2Cu3Ox." Physical Review B 46, no. 21 (1992): 14249–14252.
Abstract: We show that illumination of oxygen-deficient metallic YBa2Cu3Ox films produces a change in the Hall coefficient, an increase in the critical temperature, and a decrease in the electrical resistivity. These changes relax to equilibrium with characteristic times of the order of days, and are due to variations in both the carrier density and mobility. The relaxation times are of the same order of magnitude as the ones measured in nonilluminated oxygen-deficient films immediately after quenching.
|
|
Bud’ko, S. L., J. Guimpel, O. Nakamura, M. B. Maple, and I. K. Schuller. "Uniaxial pressure dependence of the superconducting critical temperature in RBa{2}Cu{3}O{7-δ} high-T{c} oxides." Physical Review B 46, no. 2 (1992): 1257.
|
Ferrari, H., S. O. Valenzuela, V. Bekeris, J. Guimpel, and F. de la Cruz. "Short-time magnetization in superconducting thin films." REVISTA MEXICANA DE FISICA 44 (1998): 193–195.
Abstract: We have investigated the magnetization in thin (Y;Gd)Ba2Cu3O7-delta superconducting films in the 100 μs time scale. Magnetic moment was measured with a non-conventional technique that combines the use of a pulsed magnetic field and a synchronized pulsed laser. Both virgin and magnetically cycled samples were examined and results are described within Bean's critical state model.
|
Guimpel, J., and F. de la Cruz. "Electrical resistivity of amorphous Zr70Cu30 and the Kondo like model." Solid State Communications 44, no. 7 (1982): 1045–1046.
Abstract: Electrical resistivity measurements of amorphous Zr70Cu30 as a function of the concentrations of two level systems show that a Kondo like theory cannot explain the observed temperature dependence.
|
|
Fernandes, A. A. R., J. Santamaria, S. L. Bud’ko, O. Nakamura, J. Guimpel, and I. K. Schuller. "Effect of physical and chemical pressure on the superconductivity of high-temperature oxide superconductors." Physical Review B 44, no. 14 (1991): 7601.
|
