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Author Sereni, J.G.; Kappler, J.P.
Title Magnetic and thermal properties of CeCu Type Journal Article
Year 1992 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal J. Magn. Magn. Mater.
Volume (down) 109 Issue 2-3 Pages 349-352
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Abstract Magnetic susceptibility, high field magnetization and specific heat measurements on CeCu are presented. An antiferromagnetic transition is observed at T(N) = 313 K, with some evidences of low dimensionality of the order parameter. The saturation magnetization. M(s) = 1.16-mu(B), implies that the crystalline electric field (CEF) ground state doublet is strongly magnetic, in agreement with the low temperature Curie constant C = 0.46 emu K/mol. In the high temperature limit (T > 50 K), the obtained Curie constant is C = 0.65 emu K/mol, which suggests an overall CEF splitting larger than 200 K. The entropy gain at the magnetic transition is 72% of the expected R in 2. The missing entropy is related to a specific heat anomaly with a maximum at approximately 13 K, which is attributed to magnetic fluctuations in the Ce chains. The transition temperature and the high temperature broad maximum in the specific heat are weakly affected by an applied magnetic field of 1 T.
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ISSN 0304-8853 ISBN Medium
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Notes ISI:A1992HP06000034 Approved no
Call Number BT @ hernan @ Serial 112
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Author 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 (down) 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 KAPPLER, J.P.; SCHMERBER, G.; TROVARELLI, O.; SERENI, J.G.
Title HEAVY FERMION AND INTERMEDIATE VALENCE BEHAVIOR IN CE24CO11 Type Journal Article
Year 1992 Publication JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS Abbreviated Journal
Volume (down) 108 Issue 1-3 Pages 185-186
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Abstract Low temperature specific heat and magnetic susceptibility measurements on Ce24Co11 are reported. The electronic specific heat can be decomposed into two contributions: a low temperature one (arising at T < 5 K), with a maximum of 2.2 J/K mol at 0.9 K, and another one becoming dominant at T > 5 K, characterized by a gamma(HT) = 1.8 J/K2 mol efficient. The (chi)T product changes continuously with temperature, from 0.48 emu K/mol at 2 K to 7.85 emu K/mol at 200 K. Reminding that 1 mol = 1f.u. contains 24 Ce atoms distributed in ten unequivalent crystalline sites, we interpret the experimental results as due to: one atom which behaves as a heavy fermion, and the rest as intermediate valents, with a distribution of characteristic energies governed by nine different environments. The specific heat behaviour under applied field confirms this interpretation.
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Notes ISI:A1992HH32900076 Approved no
Call Number BT @ hernan @ Serial 114
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Author Pureur, P.; Sereni, J.G.; Schaf, J.
Title Specific heat and magnetic susceptibility in YNd alloys Type Journal Article
Year 1992 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal J. Magn. Magn. Mater.
Volume (down) 104 Issue 3 Pages 1632-1634
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Abstract We report on the specific heat and dc magnetic susceptibility measurements of the YNd 4.5, 6.8 and 9.0 at % alloys. These systems present long-range SDW order just below the critical temperature. For temperatures well below T(C), the spin glass type of behavior is manifest. An interpretation is given in terms of a disorder- and frustration-induced breaking of the SDW coherence into small domains.
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Notes ISI:A1992HH32800067 Approved no
Call Number BT @ hernan @ Serial 115
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Author Fraga, G.L.F.; Brandao, D.E.; Sereni, J.G.
Title Specific heat of X2MnSn (X = Co, Ni, Pd, Cu), X2MnIn (X = Ni, Pd) and Ni2MnSb Heusler compounds Type Journal Article
Year 1991 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal J. Magn. Magn. Mater.
Volume (down) 102 Issue 1-2 Pages 199-207
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Abstract Results of low-temperature specific heat measurements (1.5-8.0 K) on X2MnSn (X = Co, Ni, Pd, Cu), X2Mnln (X = Ni, Pd) and Ni2MnSb Heusler compounds are presented. All the compounds, except the cobalt based one, exibit a lattice spectrum anomaly described by an Einstein's term (soft-phonons). For all but one compound, the experimental values of the electronic specific heat coefficients are, at least, twice as big as the theoretical estimates. For two compounds it was possible to determine the magnetic effective field on Mn nuclei.
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Notes ISI:A1991GX03900034 Approved no
Call Number BT @ hernan @ Serial 117
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Author KAPPLER, J.P.; SCHMERBER, G.; SERENI, J.G.
Title CERIUM MAGNETIC-BEHAVIOR IN CE(PD,M) WITH M = CO, NI, RH, IR, PT, CU, AG AND AU Type Journal Article
Year 1988 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal J. Magn. Magn. Mater.
Volume (down) 76-7 Issue Pages 185-186
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Notes ISI:A1988T046300057 Approved no
Call Number BT @ hernan @ Serial 124
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Author Pureur, P.; Fraga, G. L.; Brandao, D. E.; Caudron,R.; Safa, H.; Nieva, G.
Title Specific heat measurements in scandium-rare earth anisotropic spin glasses Type Journal Article
Year 1987 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal J. Magn. Magn. Mater.
Volume (down) 68 Issue 2 Pages 213-217
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Abstract We report on specific heat measurements at low temperature of the anisotropic spin glass alloys ScDy 3 at%, ScEr 4.25 at% and ScEr 10 at%. We find that at the lowest temperature range the data indicate the occurrence of an anisotropy induced gap around zero frequency in the density of states of the magnetic excitations. Moreover, some of our specific heat curves present a maximum coinciding with Tg, raising thus the question of thermal signs for a spin glass phase transition in anisotropic systems.
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Notes Approved no
Call Number BT @ gnieva @ Serial 425
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Author 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 (down) 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 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 (down) 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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Notes ISI:A1987G356900173 Approved no
Call Number BT @ hernan @ Serial 129
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Author SERENI, J.G.
Title The role of “p-like” orbitals in Ce valence instabilities Type Journal Article
Year 1985 Publication Journal of Magnetism and Magnetic Materials Abbreviated Journal J. Magn. Magn. Mater.
Volume (down) 47-48 Issue FEB Pages 228-230
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Abstract From the analysis of spectroscopical data of atomic Ce, the [f(dsp)] configuration is found to be the least energetic when the metallization enthalpy is taken into account. The p-character of the band in Ce IV compounds is discussed and the p-f hybridization proposed.
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Notes ISI:A1985AKL5200061 Approved no
Call Number BT @ hernan @ Serial 131
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