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Author (up) Sereni, J.G.; Nieva, G.; Huber, J.G.; Braun, E.; Oster, F.; Bruck, E.; Roden, B.; Wohlleben, D.
Title Evidence for 4f-instability of dilute terbium in thorium Type Journal Article
Year 1987 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal J. Magn. Magn. Mater.
Volume 63-64 Issue Pages 597-599
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Abstract We have measured the specific heat of dilute Th1?xTbx alloys (0.44 < x < 2.15 a/o), which rises linearly between 0.4 and 0.9 K with a slope of ?C/T ? 450 mJ/K2molTb followed by a Schottky anomaly with a maximum near 3.8 K. The high temperature ??T product was found to be 4% lower than that of Tb3+. The resistivity shows no minimum at low temperatures. Discussion is made in terms of non-integral valence of Tb.
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ISSN 0304-8853 ISBN Medium
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Notes ISI:A1987G356900173 Approved no
Call Number BT @ hernan @ Serial 129
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Author (up) Sereni, J.G.; Nieva, G.; Kappler, J.P.
Title ANOMALOUS CRYSTAL-FIELD EFFECTS IN THE SPECIFIC-HEAT OF CE-HEAVY FERMION COMPOUNDS Type Journal Article
Year 1987 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal J. Magn. Magn. Mater.
Volume 63-64 Issue Pages 101-103
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Notes ISI:A1987G356900031 Approved no
Call Number BT @ hernan @ Serial 128
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Author (up) SERENI, J.G.; TROVARELLI, O.
Title CORRELATION BETWEEN THE HYBRIDIZATION STRENGTH AND THE CE TO CE-LIGAND SPACING IN CET(2)X(2) COMPOUNDS Type Journal Article
Year 1995 Publication JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Abbreviated Journal
Volume 140 Issue Pages 885-886
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Abstract The hybridization strength of the Ce-4f electrons with d or p orbitals of neighbouring sites, is analyzed through the comparison of the Ce-T and Ce-X spacings in CeT(2)X(2) compounds. Four different regimes, directly related to the increase of the hybridization strength, are recognized. This systematic indicates that the Ce behaviour depends more strongly on the overlap of f-p than of f-d orbitals.
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Notes ISI:A1995QM07400073 Approved no
Call Number BT @ hernan @ Serial 100
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Author (up) Sereni, J.G.; Trovarelli, O.; Schmerber, G.; Kappler, J.P.
Title Coexistence of magnetic order and heavy fermion behavior in Ce7X3 Type Journal Article
Year 1992 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal J. Magn. Magn. Mater.
Volume 108 Issue 1-3 Pages 183-184
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Abstract Low temperature specific heat and magnetic susceptibility measurements on Ce7X3 (X = Rh, Ni) compounds are reported. Ce7Rh3 shows an onset of spontaneous magnetization at 7.2 K. About 40% of the expected R ln 2 entropy gain is found in the paramagnetic phase, related to a gamma(HT) = 1.1 J/K2 mol specific heat coefficient. In Ce7Ni3 an antiferromagnetic transition is observed at 1.7 K, superimposed to a large C(p)/T electronic contribution, described by a gamma(HT) = 0.9 J/K2 mol coefficient for T > 10 K. These results are interpreted in terms of the three different crystal sublattices of Ce. The entropy gain related to each transition allows to identify the behaviour of each sublattice. In the case of Ce7Ni3 one sublattice behaves as a heavy fermion system, with a value of C(p)/T = 3.3 J/K2 Ce at. Such a behaviour is confirmed under an applied magnetic field.
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Notes ISI:A1992HH32900075 Approved no
Call Number BT @ hernan @ Serial 113
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Author (up) Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J.
Title 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
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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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Notes ISI:000222236700179 Approved no
Call Number BT @ hernan @ Serial 162
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Author (up) Sirena, M.; Haberkorn, N.; Granada, M.; Steren, L.B.; Guimpel, J.
Title 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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Notes Approved no
Call Number BT @ jguimpel @ Serial 622
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Author (up) Sirena, M.; Steren, L.B.; Guimpel, J.
Title Magnetic after-effect in manganite films Type Journal Article
Year 2001 Publication JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Abbreviated Journal
Volume 226 Issue Pages 847-848
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Abstract The time dependence of the magnetic and transport properties on La0.6Sr0.4MnO3 films and bulk samples has been studied through magnetization and resistivity measurements. A magnetic after-effect has been observed in all samples. At low temperatures, the low-field magnetization, can be described by the function M(t) = M-c + M-d exp(-t/tau) + S(H, T)ln(t), The resistivity increases logarithmically in the same temperature range. indicating the evolution of the sample to a more disordered state. Above a characteristic temperature, this behaviour is reversed and an increase of the magnetization with time is observed. The relaxation parameters depend on the bulk or films character of the samples. In the latter case, a dependence on the film thickness was found. A direct correlation between the time dependence of the resistivity and magnetization curves in manganite compounds was found. (C) 2001 Elsevier Science B.V. All rights reserved.
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Notes ISI:000170708600308 Approved no
Call Number BT @ hernan @ Serial 174
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Author (up) Steren, L.B.; Sirena, M.; Guimpel, J.
Title 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
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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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Notes ISI:000085772100006 Approved no
Call Number BT @ hernan @ Serial 179
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Author (up) Tovar, M.; Sereni, J.G.; Pedrazzini, P.; Caneiro, A.; Prado, F.; Butera, A.; Causa, M.T.
Title Magnetization and specific heat of La doped Sr2FeMoO6 Type Journal Article
Year 2004 Publication JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Abbreviated Journal J. Magn. Magn. Mater.
Volume 272 Issue Pages 857-858
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Abstract We present high-temperature magnetization and low-temperature specific heat measurements performed on the electron doped double perovskite Sr1.7La0.3FeMoO6. We have obtained the electronic contribution to C-p, gamma = 11.5(5) mJ/mol K-2. The electronic susceptibility, derived from the magnetic measurements in the paramagnetic regime (T > T-c = 390K), was chi(e)(0) =(4.9 +/- 1.5) x 10(-4) emu/mol. Anti ferromagnetic coupling between localized and itinerant moments was inferred from the data, with a coupling constant lambda = -(475 +/- 50)mol/emu, that results in a ferromagnetic-like Curie-Weiss susceptibility with Theta = 390(5) K. These results are compared with those obtained for the undoped material. (C) 2003 Published by Elsevier B.V.
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Notes ISI:000222236700045 Approved no
Call Number BT @ hernan @ Serial 63
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Author (up) TROVARELLI, O.; SERENI, J.G.; SCHMERBER, G.; KAPPLER, J.P.
Title COEXISTENCE OF KONDO AND SPIN-GLASS BEHAVIOR IN CE4Y3NI3 Type Journal Article
Year 1995 Publication JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Abbreviated Journal
Volume 140 Issue Pages 1211-1212
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Abstract Magnetic susceptibility chi and specific heat C-p measurements on Ce4Y3Ni3 are presented. The temperature of the maximum of chi(ac)(T) and C-p(T) shifts with frequency and applied field respectively, as expected for a spin glass (SG) system. The C-p (T --> 0) dependence corresponds to that of an anisotropic SG. According to the entropy gain two Ce atoms are involved in the SG contribution and two exhibit Kondo effect.
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Notes ISI:A1995QM07400233 Approved no
Call Number BT @ hernan @ Serial 101
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