Bahrs, S., A. R. Goni, C. Thomsen, B. Maiorov, G. Nieva, and A. Fainstein. "Rare-earth dependence of photoinduced chain-oxygen ordering in RBa2Cu3O7-x (x approximate to 0.3) investigated by Raman scattering." PHYSICAL REVIEW B 65, no. 2 (2002): 024522.
Abstract: We investigated a set of oxygen – deficient RBa2Cu3O7-x (xapproximate to0.3) ceramic samples with Raman spectroscopy under resonant conditions for the defect-induced Cu-O chain related modes at 230 and 600 cm(-1). Emphasis was laid on the frequency and intensity of the modes for different rare-earth atoms, and especially on their dependence under illumination. The modes display photoinduced bleaching for all R, including the nonsuperconducting R = Pr. The dynamics of their bleaching following a temperature quench indicates similar complex relaxation processes for all samples. A simple stretched exponential with a common beta = 0.36+/-0.04 and a distribution of time constants ranging from 50 to 1400 s describes our data well. We discuss our results in connection to photoinduced chain-oxygen ordering in oxygen-deficient superconductors.
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Maiorov, B., A. V. Silhanek, F. De la Cruz, and E. Osquiguil. "Comment on “strong vortex liquid correlation from multiterminal measurements on untwinned YBa2Cu3O7-? single crystals”." Physical Review Letters 88, no. 13 (2002): 1397031.
Abstract: Multiterminal measurements using experimental technique on twinned and untwinned YBa2Cu3O7-? crystals were presented. Inhomogeneous current distribution acting upon an uncorrelated vortex system showed that the dissipation of voltage at the top was larger than at the bottom. The behavior of the current voltage curves showed that the result Vtop = Vbot was a consequence of the limited voltage sensitivity.
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Maiorov, B., A. V. Silhanek, F. De la Cruz, E. Osquiguil, A. Rydh, and Rapp. "Comment on “strong vortex liquid correlation from multiterminal measurements on untwinned YBa2Cu3O7-? single crystals” [2] (multiple letters)." Physical Review Letters 88, no. 13 (2002).
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Valenzuela, S. O., B. Maiorov, E. Osquiguil, and V. Bekeris. "Elastic-to-plastic crossover below the peak effect in the vortex solid of YBa2Cu3O7 single crystals." Physical Review B – Condensed Matter and Materials Physics 65, no. 6 (2002): 605041–605044.
Abstract: We report on transport and ac susceptibility studies below the peak effect in twinned YBa2Cu3O7 single crystals. We find that disorder generated at the peak effect can be partially inhibited by forcing vortices to move with an ac driving current. The vortex system can be additionally ordered below a well-defined temperature where elastic interactions between vortices overcome pinning-generated stress and a plastic-to-elastic crossover seems to occur. The combined effect of these two processes results in vortex structures with different mobilities that give place to history effects.
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Bahrs, S., A. R. Goni, B. Maiorov, G. Nieva, A. Fainstein, and C. Thomsen. "Raman-study of photoinduced chain-oxygen ordering in RBa2Cu3O7-delta." IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 13, no. 2 (2003): 3192–3195.
Abstract: We investigated Raman-forbidden signals in RBa2Cu3O7-delta with R = Y or Pr, which lose intensity under illumination at low temperatures. These defect-induced,peaks are only visible in oxygen-deficient material and for light polarized parallel to the copper-oxygen chains along the material's b-axis. In a first, two-laser based experiment we established that the bleaching effect of the light is polarization dependent as well. From this and other known properties we conclude that the signal is connected to the copper-oxygen chains, reflecting their state of disorder, and is thus closely related to aging and to the persistent photoconductivity effect in the material. In a second set of experiments we followed the temperature dependence of the Raman spectra and the intensity decrease.
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Maiorov, Boris A. "Transición de fase y dinámica de vórtices en YBa2Cu3O7-δ." Ph.D. thesis, , 2003.
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Granada, M., B. Maiorov, M. Sirena, L. B. Steren, and J. Guimpel. "Hall effect in La0.6Sr0.4MnO3 thin films." JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272 (2004): 1836–1838.
Abstract: We studied the temperature and thickness dependence of the transport properties of La0.6Sr0.4MnO3 films. Hall voltage and magnetoresistance measurements on 10 and 150 nm thick films were performed with this porpose. From the ordinary Hall component, we calculated the density of carriers, which has hole-character and is systematically lower than that expected from the chemical composition of the manganite in both samples. Localization effects observed at low temperature in the resistivity of the thinner film, associated with the substrate-induced disorder, are correlated with a decrease of the density of carriers. (C) 2003 Elsevier B.V. All rights reserved.
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Bahrs, S., A. R. Goni, C. Thomsen, B. Maiorov, G. Nieva, and A. Fainstein. "Light-induced oxygen-ordering dynamics in (Y,Pr)Ba2Cu3O6.7: A Raman spectroscopy and Monte Carlo study." PHYSICAL REVIEW B 70, no. 1 (2004): 014512.
Abstract: We investigated the time and temperature dependence of photobleaching effects in RBa2Cu3O7-delta single crystals (R=Y,Pr) by Raman spectroscopy and Monte Carlo simulations based on the asymmetric next-nearest-neighbor Ising model. In a temperature range between 40 and 300 K the bleaching slows down on cooling, displaying a pronounced change in dynamics around 160 K for R=Y. To model this behavior we extended the Ising model by introducing a single energy barrier which impedes oxygen movement in the plane unless the oxygen atoms are excited by light. We obtain a time- and temperature-dependent development of superstructures under illumination with the fastest change at intermediate model temperatures. The chain-fragment development in the simulation thus matches the experimental low-temperature dynamics of Raman photobleaching, providing further support for oxygen reordering in the chain plane being at the origin of Raman photobleaching and related effects.
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Rigal, L. B., D. C. Schmadel, H. D. Drew, B. Maiorov, E. Osquiguil, J. S. Preston, R. Hughes, and G. D. Gu. "Magneto-optical evidence for a gapped Fermi surface in underdoped YBa 2Cu3O6+x." Physical Review Letters 93, no. 13 (2004).
Abstract: An evidence presented that supports partial gapping of the Fermi surface by a measurement of the Hall frequency from high frequency magneto-optical measurements on underdoped YBa2Cu3O6+x (YBCO) was discussed. It was found that the Hall frequency was obtained independently of the unknown k-space dependence of the carrier scattering rates that complicated the dc Hall effect. It was observed that the frequency dependence of the Hall angle was Drude-like and indicated a quasielastic relaxation process for optimal and underdoped samples. The results show that there was an increase of the Hall frequency in the pseudogap state.
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Maiorov, B., and E. Osquiguil. "Bose-glass-like phases in oriented-twin YBa2Cu3O7-? crystals." Journal of Low Temperature Physics 135, no. 1-2 (2004): 131–134.
Abstract: We experimentally study the dynamical response of the superconducting vortex system near the solid-liquid transition by applying forces parallel and perpendicular to a planar random defect array. Our results show that for magnetic fields above a certain critical field Hcr'? 4 T the solid glassy vortex phase in YBa2Cu3O7-? crystals with oriented twin planes does not correspond to the so-called Bose-glass phase.
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