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Sereni, J. G., G. Schmerber, and J. P. Kappler. "Thermodynamic Behavior of Ce Compounds Close to a T->0 Critical Point." IEEE Transactions on Magnetics 49, no. 8 (2013): 4647–4651.
Abstract: There is a reduced group of Ce very heavy Fermions (VHF) which do not order magnetically down to at least T ≈ 500 mK because they are very close to a Tord = 0 critical point. These compounds are at the top of the limT→ 0 Cm/T specific heat values because they collect very high density of low energy excitations. From the analysis of Cm(T)/T and entropy Sm(T) dependencies performed on selected CePd3Mx ternaries (where M = B and Be) a quantitative evaluation of an upper limit for the density of excitations can be proposed. These observations exclude any evidence of Cm(T)/T divergency as T→ 0 in agreement with thermodynamic laws. A comparison with selected Yb-base VHF supports these features.
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Kappler, J. P., P. Lehmann, G. Schmerber, G. Nieva, and J. G. Sereni. "Magnetic properties of the Ce-Rh binary phases." Journal de Physique Colloques 49, no. C8 (1988): 721–722.
Abstract: Crystallographic, magnetic and resistivity studies on the Ce-Rh binary phases clearly define two Ce ground state regions : i) CeRh3, CeRh2 and CeRh as intermediate valence compounds and ii) Ce5Rh4, Ce3Rh2 Ce5Rh3 and Ce7Rh3 with magnetic transitions at low temperature.
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Braghta, A., G. Schmerber, A. Derory, J. G. Sereni, and J. P. Kappler. "Magnetic and thermal properties of Ce2Pd2Sn." Journal of Magnetism and Magnetic Materials 320, no. 6 (2008): 1141–1145.
Abstract: X-ray diffraction, susceptibility and specific heat studies on ternary Ce2Pd2Sn intermetallic compound and on its isostructural nonmagnetic compound La2Pd2Sn are reported. On Ce2Pd2Sn in absence of magnetic field, we confirm the existence of two magnetic transitions at T-N = 4.8K (antiferromagnetic transition) and T-C = 2.2K (ferromagnetic transition) and the specific heat results, measured down to 0.5 K, allow to recognize the transition at 2.2K as a first-order transition. A description based on molecular field calculations for the S = 1/2 resonant level model leads to a characteristic Kondo T-K of about 3K. (C) 2007 Elsevier B.V. All rights reserved.
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TROVARELLI, O., J. G. SERENI, G. SCHMERBER, and J. P. KAPPLER. "COEXISTENCE OF KONDO AND SPIN-GLASS BEHAVIOR IN CE4Y3NI3." JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 140 (1995): 1211–1212.
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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Kappler, J. P., G. Schmerber, and J. G. Sereni. "Magnetic and thermal properties of Ce5Rh3." Journal of Magnetism and Magnetic Materials 115, no. 2-3 (1992): 241–244.
Abstract: Magnetic susceptibility, high field magnetization and specific heat measurements on Ce5Rh3 are reported. Two antiferromagnetic transitions are observed at T(N)=4.5 K and T(N)'=2.6 K. The magnetization curve at 1.5 K reveals a nontrivial magnetic structure in this compound, with a saturation magnetization of 0.72mu(B). The high temperature Curie constant (0.64 emu K/mol), the Curie-Weiss constant (THETA(p)=-45 K) and the entropy related with the magnetic transitions (DELTAS(m)=0.8 R In 2) indicate the presence of a Kondo-type component in the ground state of Ce5Rh3.
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Sereni, J. G., O. Trovarelli, G. Schmerber, and J. P. Kappler. "Coexistence of magnetic order and heavy fermion behavior in Ce7X3." Journal of Magnetism and Magnetic Materials 108, no. 1-3 (1992): 183–184.
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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KAPPLER, J. P., G. SCHMERBER, O. TROVARELLI, and J. G. SERENI. "HEAVY FERMION AND INTERMEDIATE VALENCE BEHAVIOR IN CE24CO11." JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 108, no. 1-3 (1992): 185–186.
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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KAPPLER, J. P., G. SCHMERBER, and J. G. SERENI. "CERIUM MAGNETIC-BEHAVIOR IN CE(PD,M) WITH M = CO, NI, RH, IR, PT, CU, AG AND AU." Journal of Magnetism and Magnetic Materials 76-7 (1988): 185–186.
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Sereni, J. G., G. L. Nieva, G. Schmerber, and J. P. Kappler. "EVIDENCES FOR UNCONVENTIONAL SUPERCONDUCTIVITY IN RARE-EARTH INTERMETALLICS." Modern Physics Letters B 3, no. 16 (1989): 1225–1231.
Abstract: The specific heat of CeRu2 and La5Rh4 of the superconducting state does not follow a BCS-exponential temperature dependence, but a T2 law. At very low temperature (T = 0.1 Tc), CeRu2 shows a linear T dependence, which corresponds to a constant density of states. The experimental results are well described by the theoretical predictions for an axial state (CeRu2) and polar state (La5Rh4) superconductors. The small Sommerfeld coefficient of La5Rh4(? = 3.4 mJ/K2 La at.) excludes this compound from the heavy fermion superconductors.
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Sereni, J. G., O. Trovarelli, J. Schaf, G. Schmerber, and J. P. Kappler. "Extremely Low Density of States in CePd7." Modern Physics Letters B 5, no. 18 (1991): 1249–1253.
Abstract: The low temperature specific heat and magnetic susceptibility measurements, up to room temperature, on CePd7 are reported. The Sommefeld coefficient gamma and the Pauli susceptibility chio were found to have the lowest values within the Ce compounds: gamma = 9.8 mJ/mole K2 and chio = 0.14 × 10-3 emu/mole. The ratio chio/gamma = 0.014 emu K2/J is that of a free electron, instead of an intermediate valence system (0.036 emu K2/J). Such a value suggests complete delocalization of the Ce 4f electrons.
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