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Author (up) Bahrs, S.; Bruchhausen, A.; Goni, A.R.; Nieva, G.; Fainstein, A.; Fleischer, K.; Richter, W.; Thomsen, C.
Title Effect of light on the reflectance anisotropy and chain-oxygen related Raman signal in untwinned, underdoped crystals of YBa2Cu3O7-delta Type Journal Article
Year 2006 Publication JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS Abbreviated Journal
Volume 67 Issue 1-3 Pages 340-343
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Abstract Recent studies of the optical anisotropy of a detwinned, underdoped YBa2Cu3O7-delta-crystal showed that illumination-induced change and recovery in the surface reflectance can be traced on a time scale of hours. This effect of light is also known from Raman bleaching and electrical transport and shares features of the oxygen reordering processes above room temperature. We report temperature-dependent studies of the optical anisotropy using reflectance anisotropy spectroscopy and present time-dependent data for the optical transitions at 2.2 and 4.4 eV. We compare our results to Raman bleaching and discuss them within the picture of superstructure patterns and oxygen-defect reordering in underdoped YBa2Cu3O7-delta. (c) 2005 Elsevier Ltd. All rights reserved.
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ISSN 0022-3697 ISBN Medium
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Notes ISI:000236746600084 Approved no
Call Number BT @ hernan @ Serial 203
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Author (up) Bahrs, S.; Muller, S.; Rubhausen, M.; Schulz, B.; Goni, A.R.; Nieva, G.; Thomsen, C.
Title Anisotropic ultraviolet raman resonance in underdoped YBa2Cu3O6.7 Type Journal Article
Year 2006 Publication PHYSICAL REVIEW B Abbreviated Journal
Volume 74 Issue 2 Pages 024519
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Abstract We report an inverse Raman-bleaching anomaly of oxygen-vacancy-activated phonons in underdoped YBa2Cu3O6.7 excited in resonance at 4.1 eV. These modes are closely related to modes that photobleach under visible excitation. The resonance and selection rules match the prediction from the ab in-plane anisotropy of the dielectric function, as does their growth of intensity under illumination. These properties support the oxygen-vacancy-reordering model for photoinduced changes in underdoped YBa2Cu3O7-delta. We suggest that a similar coupling to anisotropic electronic resonances is responsible for the recently discovered ab anisotropies in the phonon dispersion.
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Series Volume Series Issue Edition
ISSN 1098-0121 ISBN Medium
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Notes ISI:000239426600091 Approved no
Call Number BT @ hernan @ Serial 202
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Author (up) Deppe, M.; Pedrazzini, P.; Caroca-Canales, N.; Gelbel, C.; Sereni, J.G.
Title Investigations of CePd1-xRhx single crystals located near a ferromagnetic quantum critical point Type Journal Article
Year 2006 Publication PHYSICA B-CONDENSED MATTER Abbreviated Journal
Volume 378-380 Issue Pages 96-97
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Abstract Investigations of CePd1-xRhx polycrystals have revealed a continuous transition from a ferromagnetic state at x = 0 to an intermediate valence state at x = 1 and evidenced non-Fermi liquid behavior near the critical concentration x(c) approximate to 0.85 where T-C is continuously suppressed to T = 0 K. We present here first results of specific heat and magnetization measurements on CePd1-xRhx single crystals with composition close to the critical point. They confirm the results obtained on polycrystals and reveal a rather low magnetic anisotropy, despite the orthorhombic structure. (c) 2006 Elsevier B.V. All rights reserved.
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Series Volume Series Issue Edition
ISSN 0921-4526 ISBN Medium
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Notes ISI:000238426600033 Approved no
Call Number BT @ hernan @ Serial 56
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Author (up) Fasano, Y.; Seta, M.D.; Menghini, M.; Pastoriza, H.; Cruz, F. de la
Title Effect of vortex dimensionality on elastic and plastic symmetry transformations induced in vortex matter Type Journal Article
Year 2006 Publication Journal of Physics and Chemistry of Solids Abbreviated Journal
Volume 67 Issue Pages 395-398
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Abstract We analyse the role played by vortex dimensionality in structural transformations induced at the surface of bulk Bi$2$Sr$2$CaCu$8$ (extremely anisotropic) and NbSe$2$ (moderately anisotropic) vortex crystals interacting with two-dimensional square pinning structures. The observation of alternating floating and distorted hexagonal domains induced in the NbSe$2$ vortex structure contrasts with the square one induced in Bi$2$Sr$2$CaCu$8$. Despite vortex-vortex interaction energy being similar in both materials, the different elastic characteristics and the dissimilar vortex solidification mechanisms are responsible for the plastic and elastic structural transformations detected in Bi$2$Sr$2$CaCu$8$ and NbSe$_2$, respectively.
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Notes Approved no
Call Number BT @ hernan @ fasano05 Serial 20
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Author (up) Giordano, J.L.; Luzuriaga, J.; Badía-Majós, A.; Nieva, G.; Ruiz-Tagle, I. A.
Title Magnetization collapse in polycrystalline YBCO under transport current cycles Type Journal Article
Year 2006 Publication Superconducting Science and Technology Abbreviated Journal Supercond. Sci. Technol.
Volume 19 Issue 4 Pages 385-391
Keywords
Abstract We report measurements of the hysteretic magnetization of YBCO under superimposed transport current cycles, together with numerical simulations of magnetization and current density profiles in the corresponding parallel configuration. Field cooled (FC) and zero-field-cooled (ZFC) experiments were carried out on polycrystalline YBa2Cu3O7?x cylinders, with both the applied magnetic field and transport current in the axial direction, and the current cycled several times, around and above the dissipative threshold. As in previously reported multicomponent field configuration experiments, the magnetization is seen to collapse to a more stable state both in FC and ZFC, because of the interplay between the shielding and transport currents. The results of our numerical simulations are in good qualitative agreement with the measurements, and the competition between shielding and transport due to vortex-pinning interactions and equilibrium magnetization effects are shown to play an important role in the range of our experiments.
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ISSN 0953-2048 ISBN Medium
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Notes Approved no
Call Number BT @ gnieva @ Serial 467
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Author (up) Giordano, J.L.; Luzuriaga, J.; Ruíz-Tagle,; NIEVA, G.; Badía-Majós,
Title Magnetization measurements of hard superconductors under dissipative transport Type Journal Article
Year 2006 Publication Journal of Physics: Conference Series Abbreviated Journal J. Phys. Conf. Ser.
Volume 43 Issue 1 Pages 663-666
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Abstract The hysteretic magnetic flux dynamics of ceramic type-II superconductors under superimposed transport current cycles has been investigated. Field cooled and zero field cooled experiments were carried-out on polycrystalline YBa 2Cu3O7-x cylinders by using both temperature and applied field control, to drive the sample into the semi-reversible granular regime. The transport current magnitude was near and above the dissipative threshold. The interplay between shielding and transport due to vortex-pinning interactions, equilibrium magnetization effects, and diamagnetic/paramagnetic relaxation phenomena are shown to play an important role in the range of practical applications.
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ISSN 17426588 (ISSN) ISBN Medium
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Notes Export Date: 28 April 2009; Source: Scopus; Art. No.: 162; doi: 10.1088/1742-6596/43/1/162; Language of Original Document: English; Correspondence Address: Giordano, J.L.; Departamento de Ciencias de la Ingenier Approved no
Call Number BT @ luzuriag @ Serial 471
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Author (up) Gomez, M.E.; Campillo, G.; Ramirez, J.G.; Prieto, P.; Hoffmann, A.; Guimpel, J.; Haberkorn, N.; Condo, A.; Lovey, F.
Title Magnetotransport properties in epitaxial exchange-biased La2/3Ca1/3MnO3/La1/3Ca2/3MnO3 superlattices Type Journal Article
Year 2006 Publication IEEE Transactions on Magnetics Abbreviated Journal IEEE Trans. Magn.
Volume 42 Issue 10 Pages 2981-2983
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Abstract Superlattices of ferromagnetic (F) and antiferromagnetic (AF) oxide materials have attracted increased attention given the exchange bias or exchange anistropy phenomenon. Research on magnetic oxide superlattices has focused toward the technological goals of increasing magnetores stance in lower applied magnetic fields and more useful temperature ranges for various applications. Superlattices of F-LCMO and AF-LCMO layers were grown on (001)-oriented SrTiO3 substrates. We studied the temperature dependence of magnetotransport properties for a series of [AF-LCMO (7.6 nm)/F-LCMO (t(F))](N) superlattices as a function of the ferromagnetically doped layer thickness, t(F), while the antiferromagnetic (AF) layer thickness, t(AF), was kept constant. Magnetotransport measurements at different temperatures were done on a series of [AF(7.6 nm)IF(t(F))](N) superlattices. The ZFC resistance has a maximum at negative fields, for all multilayers, with descending fields (from 1 to -1 kOe). In all samples a shift along the field axis of the FC loop with respect to that of the ZFC loop is observed. The H-ex values determined from these displacements of the FC loops of the magnetoresistance loops increase when temperature decreases and its magnitude also depends on the ferromagnetic layer thickness.
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ISSN 0018-9464 ISBN Medium
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Notes ISI:000240888700241 Approved no
Call Number BT @ hernan @ Serial 153
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Author (up) Gonzalez, E.M.; Sefrioui, Z.; Maiorov, B.; Osquiguil, E.; Santamar
Title Effects of structural microdomains on the vortex correlation length in a-axis oriented EuBa2Cu3O7 thin films Type Journal Article
Year 2006 Publication Journal of Physics and Chemistry of Solids Abbreviated Journal J Phys Chem Solids
Volume 67 Issue 1-3 Pages 399-402
Keywords A. Superconductors; A. Thin films; B. Epitaxial growth; D. Superconductivity; D. Transport properties; Activation energy; Anisotropy; Epitaxial growth; Europium compounds; Magnetron sputtering; Superconductivity; Thin films; Transport properties; Anisotropic superconductors; Domain boundaries; Structural microdomains; Vortex correlation; Superconducting materials
Abstract We have grown a-axis oriented EuBa2Cu3O7 thin films on SrTiO3 (001) substrates using a magnetron sputtering technique. In these films the CuO2 planes are aligned parallel to the substrates. The film microstructure shows microdomains. The microdomains are grains with a 90
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ISSN 00223697 (ISSN) ISBN Medium
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Notes Export Date: 17 April 2009; Source: Scopus; CODEN: JPCSA; doi: 10.1016/j.jpcs.2005.10.093; Language of Original Document: English; Correspondence Address: Vicent, J.L.; Departamento F Approved no
Call Number BT @ osquigui @ Serial 364
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Author (up) Hoffmann, A.; Nieva, G.; Guimpel, J.; Bruynseraede, Y.; Santamaria, J.; Lederman, D.; Schuller, I.K.
Title Comment on “Photoemission study of YBa2Cu3Oy thin films under light illumination” Type Journal Article
Year 2006 Publication PHYSICAL REVIEW LETTERS Abbreviated Journal
Volume 97 Issue 11 Pages 119701
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ISSN 0031-9007 ISBN Medium
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Notes ISI:000240545600075 Approved no
Call Number BT @ hernan @ Serial 154
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Author (up) Kasama, T.; Moreno, M.S.; Dunin-Borkowski, R.E.; Newcomb, S.B.; Haberkorn, N.; Guimpel, J.; Midgley, P.A.
Title Characterization of the magnetic properties of a GdBa2Cu3O7/La0.75Sr0.25MnO3 superlattice using off-axis electron holography Type Journal Article
Year 2006 Publication Applied Surface Science Abbreviated Journal Appl. Surf. Sci.
Volume 252 Issue 11 Pages 3977-3983
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Abstract Off-axis electron holography is used to characterize the magnetic properties of a GdBa2Cu3O7/La0.75Sr0.25MnO3 superlattice below the Curie temperature of the manganite layers, in both cross-sectional and plan-view geometry. The samples were prepared for electron microscopy using focused ion beam milling. Differences between the magnetic properties of successive manganite layers are observed in the cross-sectional sample. Magnetic ripple contrast and weakly magnetic regions are observed in plan-view geometry. Although the results may be affected by sample preparation for electron microscopy, the observed differences between the magnetic properties of the manganite layers are consistent between the different samples examined. (c) 2005 Elsevier B.V. All rights reserved.
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Series Volume Series Issue Edition
ISSN 0169-4332 ISBN Medium
Area Expedition Conference
Notes ISI:000236835200013 Approved no
Call Number BT @ hernan @ Serial 155
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