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Author Causa, M.T.; Dutrus, S.M.; Fainstein, C.; Nieva, G.; Sanchez, R.; Steren, L.B.; Tovar, M.; Zysler, R.; Oseroff, S.B.; Vier, D.C.; Schultz, S.; Fisk, Z.; Smith, J.L.
Title (up) Magnetic ordering in dilute GdxEu1−xBa2Cu3O7−δ superconductors Type Journal Article
Year 1988 Publication Physica C: Superconductivity Abbreviated Journal Physica C
Volume 153 Issue Pages 188-189
Keywords
Abstract We have measured the specific heat of GdxEu1−xBa2Cu3O7−δ (0 ≤ × ≤ 1). The data show a λ-type anomaly at high concentrations and a broad Schottky type anomaly at intermediate and low concentrations. We compare this behavior with theoretical predictions for a 2-dimensional Ising system.
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Notes Approved no
Call Number BT @ gnieva @ Serial 432
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Author Sirena, M.; Steren, L.B.; Guimpel, J.
Title (up) Magnetic relaxation in bulk and film manganite compounds Type Journal Article
Year 2001 Publication PHYSICAL REVIEW B Abbreviated Journal
Volume 64 Issue 10 Pages
Keywords
Abstract We have investigated the time dependence of the magnetic and transport properties of La0.6Sr0.4MnO3 films and bulk samples. A significant magnetic aftereffect has been observed in all the samples through magnetization and resistivity measurements. The relaxation effects can be described by the addition of a logarithmic to an exponential contribution. The weight of each contribution is strongly temperature dependent, with a relaxation that is predominantly logarithmic at low temperatures (T<30 K) and exponential at high temperatures (T>100 K). As the film thickness is decreased the magnetic relaxation becomes more important and the magnetic viscosity of the system increases. These results point out the important role of structural defects in the magnetic relaxation of the samples.
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ISSN 0163-1829 ISBN Medium
Area Expedition Conference
Notes ISI:000170978400046 Approved no
Call Number BT @ hernan @ Serial 173
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Author Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J.
Title (up) Metal-insulator transition induced by postdeposition annealing in low doped manganite films Type Journal Article
Year 2009 Publication JOURNAL OF APPLIED PHYSICS Abbreviated Journal
Volume 105 Issue 3 Pages
Keywords
Abstract We studied the transport and magnetic properties of low-doped manganite films after different oxygenation processes. The oxygen content was adjusted by postdeposition annealing at different oxygen pressures and annealing times. For all the samples we observed an increase in the Curie temperature and the remnant magnetization with the oxygen content. In general, for decreasing number of oxygen vacancies, samples under expansive strain become more homogeneous and their electrical resistivity decreases. A metal-insulator transition is induced in highly oxygenated films grown on SrTiO3, probably related to a shift of the mobility edge crossing below the Fermi energy. We found that the oxygenation dynamics depend critically on the strain field induced by the substrates and also on the Sr doping concentration.
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ISSN 0021-8979 ISBN Medium
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Notes ISI:000263409700057 Approved no
Call Number BT @ hernan @ Serial 143
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Author Sirena, M.; Granada, M.; Steren, L.B.; Guimpel, J.
Title (up) Metal/insulator manganite multilayers Type Journal Article
Year 2002 Publication PHYSICA B-CONDENSED MATTER Abbreviated Journal
Volume 320 Issue 1-4 Pages 172-174
Keywords
Abstract We have studied the transport and magnetic properties of strongly textured metal/insulator La1-xSrxMnO3 (x = 0.4, 0.1) bilayers and trilayers, grown by DC magnetron sputtering over MgO and SrTiO3 substrates. The multilayers present transport properties similar to those of the La0.6Sr0.4MnO3 films, being very sensitive to deposition conditions. Magnetic multilayers show a metal-insulator transition around T-c (similar to250 K) and colossal magnetoresistance which is maximum around T-c. No extrinsic magnetoresistance associated with the multilayered structure was observed, probably due to the presence of ferromagnetic coupling between the metallic layers, as suggested by magnetization measurements. (C) 2002 Elsevier Science B.V. All rights reserved.
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ISSN 0921-4526 ISBN Medium
Area Expedition Conference
Notes ISI:000177607700047 Approved no
Call Number BT @ hernan @ Serial 170
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Author Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J.
Title (up) Oxygen and disorder effect in the magnetic properties of manganite films Type Journal Article
Year 2004 Publication JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Abbreviated Journal
Volume 272 Issue Pages 1171-1173
Keywords
Abstract We have made a systematic study of the magnetic properties of low doped manganite films submitted to different oxygenation treatments. We have found that oxygenation dynamics depends critically of the strain field in the sample. The T-C and the Mr increase as the oxygen content is increased. A decrease of the coercive field of the LSMO-STO films was observed, indicating that annealing treatments increase the oxygen content reducing oxygen vacancies. (C) 2004 Elsevier B.V. All rights reserved.
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Series Editor Series Title Abbreviated Series Title
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ISSN 0304-8853 ISBN Medium
Area Expedition Conference
Notes ISI:000222236700179 Approved no
Call Number BT @ hernan @ Serial 162
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Author Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J.
Title (up) Oxygen and disorder effect in the magnetic properties of manganite films Type Journal Article
Year 2004 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal Proceedings of the International Conference on Magnetism (ICM 2003)
Volume 272-276, Part 2 Issue Pages 1171-1173
Keywords Manganite fims; Oxigenation; Magnetic properties
Abstract We have made a systematic study of the magnetic properties of low doped manganite films submitted to different oxygenation treatments. We have found that oxygenation dynamics depends critically of the strain field in the sample. The TC and the Mr increase as the oxygen content is increased. A decrease of the coercive field of the LSMO-STO films was observed, indicating that annealing treatments increase the oxygen content reducing oxygen vacancies.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-8853 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number BT @ jguimpel @ Serial 622
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Author Sirena, M.; Kaul, E.; Pedreros, M.B.; Rodriguez, C.A.; Guimpel, J.; Steren, L.B.
Title (up) Structural, magnetic and electrical properties of ferromagnetic/ferroelectric multilayers Type Journal Article
Year 2011 Publication Journal of Applied Physics Abbreviated Journal J. Appl. Phys.
Volume 109 Issue 12 Pages 123920
Keywords atomic force microscopy; barium compounds; electrical conductivity; ferroelectric materials; ferromagnetic materials; lanthanum compounds; magnetic multilayers; magnetisation; multiferroics; sputter deposition; strontium compounds; superlattices; texture; tunnelling; X-ray diffraction
Abstract The La0.75Sr0.25MnO3 (LSMO)/Ba0.7Sr0.3TiO3 (BSTO) superlattices and bilayers, where LSMO is ferromagnetic and BSTO is ferroelectric, were grown by dc sputtering. X-ray diffraction indicates that the samples present a textured growth with the c axis perpendicular to the substrate. Magnetization measurements show a decrease of the sample’s magnetization for decreasing ferromagnetic thickness. This effect could be related to the presence of biaxial strain and a magnetic dead layer in the samples. Conductive atomic force microscopy indicates that the samples present a total covering of the ferromagnetic layer for a ferroelectric thickness higher than four unit cells. Transport tunneling of the carriers seems to be the preferred conduction mechanism through the ferroelectric layer. These are promising results for the development of multiferroic tunnel junctions.
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Call Number BT @ jguimpel @ Serial 606
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Author Haberkorn, N.; Guimpel, J.; Steren, L.B.; Campillo, G.; Saldarriaga, W.; Gomez, M.E.
Title (up) Structure of high-T-c/manganite perovskite superlattices Type Journal Article
Year 2003 Publication JOURNAL OF APPLIED PHYSICS Abbreviated Journal
Volume 94 Issue 5 Pages 3011-3014
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Abstract We study the crystalline and interface structure of RBa2Cu3O7/La(1-x)A(x)MnO(3) superlattices (R=Y, Gd; A=Ca, Sr) grown on mismatched MgO substrates by means of nondestructive x-ray diffraction. The diffraction patterns are adjusted to a model of the structure which includes interface roughness and interdiffusion. Our results show that these disorder mechanisms cannot be neglected and should be taken into account to understand the physical properties of these superlattice. (C) 2003 American Institute of Physics.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0021-8979 ISBN Medium
Area Expedition Conference
Notes ISI:000184844200032 Approved no
Call Number BT @ hernan @ Serial 167
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Author Steren, L.B.; Sirena, M.; Guimpel, J.
Title (up) Substrate effect on the magnetic behavior of manganite films Type Journal Article
Year 2000 Publication JOURNAL OF APPLIED PHYSICS Abbreviated Journal
Volume 87 Issue 9 Pages 6755-6757
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Abstract The film thickness (t) dependence of the magnetic properties of La0.6Sr0.4MnO3 (LSMO) films grown on (001) MgO and (001) SrTiO3 substrates has been studied. Hysteresis loops measured at low temperature show a smooth increase of the retentivity accompanied by a decrease of the coercitive field as the film thickness increases. The increase of coercitivity with decreasing t can be interpreted in terms of a change in the domain structure of the films mainly due to an augmentation of domain pinning defects. The magnetic anisotropy has been measured using ferromagnetic resonance (FMR). A volume (VA) and a surface (SA) anisotropy contribution have been deduced from FMR angular dependence studies for both series of samples. In the LSMO films grown on MgO a VA component that corresponds to an easy-axis perpendicular to the plane of the films has been found while in contrast, the LSMO films grown on SrTiO3 present an easy-plane anisotropy. The SA is positive for both series favoring a perpendicular magnetic anisotropy. The measured magnetic anisotropy has been assigned to substrate-induced effects. (C) 2000 American Institute of Physics. [S0021-8979(00)55708-9].
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Language Summary Language Original Title
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ISSN 0021-8979 ISBN Medium
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Notes ISI:000086728800281 Approved no
Call Number BT @ hernan @ Serial 178
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Author Steren, L.B.; Sirena, M.; Guimpel, J.
Title (up) Substrate influence on the magnetoresistance and magnetic order in La0.6Sr0.4MnO3 films Type Journal Article
Year 2000 Publication JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Abbreviated Journal
Volume 211 Issue 1-3 Pages 28-34
Keywords
Abstract We report structural, magnetic and transport measurements on La0.6Sr0.4MnO3 thin films grown on MgO and TiSrO3 substrates with thickness varying from 5 to 500 nm. We find that the lattice mismatch between substrates and films affects the morphology and induced-strains of the films. We show that these two different effects strongly influence the ferromagnetic order, the metal-insulator transition, the localization of the current carriers and the magnetoresistance of these materials. (C) 2000 Elsevier Science B.V. All rights reserved.
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Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-8853 ISBN Medium
Area Expedition Conference
Notes ISI:000085772100006 Approved no
Call Number BT @ hernan @ Serial 179
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