Pedrazzini, P., M. G. Berisso, O. Trovarelli, J. G. Sereni, and C. Geibel. "Evolution of the ground state in the ternary system CeT2Si2 (T=Cu, Rh and Pd)." Journal of Low Temperature Physics 135, no. 1-2 (2004): 143–146.
Abstract: The heavy fermion compounds CeCu2Si2, CeRh2Si2 and CePd2Si2 have been intensively investigated due to the non-conventional relation between superconductivity and magnetism. We have studied these compounds as constituents of a ternary system, where the Ce(RhxCu1-x)(2)Si-2, Ce(PdyRh1-y)(2)Si-2 and Ce(CuzPd1-z)(2)Si-2 alloys span the sides of a triangle with the respective stoichometric compounds at each vertex. In this article we discuss the evolution of the ground state throughout this ternary system, and we analyse (by means of the electrical resistivity) the influence of doping-induced disorder on the Kondo and magnetic ordering temperatures.
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Pedrazzini, P., D. Jaccard, M. Deppe, C. Geibel, and J. G. Sereni. "Multiprobe high-pressure experiments in CePd0.6Rh0.4 and CePd3." Physica B: Condensed Matter 404, no. 19 (2009): 2898–2903.
Abstract: Results of recent multiprobe high-pressure experiments on ferromagnetic CePd0.6Rh0.4 and intermediate-valent CePd3 are presented. Simultaneous resistivity (ρ), thermopower (S), and ac heat capacity measurements show that the long-range ferromagnetic state of CePd0.6Rh0.4 vanishes in the proximity of a sharp valence-crossover pressure , i.e. before reaching a quantum critical point. However, a magnetic signal that is progressively suppressed is still detected at higher pressures. For CePd3, the results of simultaneous ρ(T,p) and S(T,p) measurements up to and down to the mK temperature range show a surprisingly weak pressure dependence.
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Pedrazzini, P., G. Schmerber, M. G. Berisso, J. P. Kappler, and J. G. Sereni. "Magnetic and superconducting properties of A(7)B(3) compounds (A = Th or La and B=Ni, Co, Fe or Pd, Rh, Ru)." PHYSICA C 336, no. 1-2 (2000): 10–18.
Abstract: High-temperature magnetization, low temperature specific heat, and ac-susceptibility measurements on Th7X3 (X = Ni, Co, and Fe) and La(7)Z(3) (Z = Pd, Rh, and Ru) superconductors are presented. The magnetic behaviour of the Th7X3 group has the characteristics of Pauli paramagnets. The La(7)Z(3) group also shows Pauli paramagnetism for Z = Pd and Ru, and signs of spin fluctuations for La7Rh3. Specific heat (C-p) measurements indicate a conventional BCS behaviour for La7Pd3 and La7Rh3, like that of the previously measured Th7X3 superconductors. in the case of La7Ru3, the reduced specific heat jump at the transition, the anomalous temperature dependence of C-p under magnetic field and a large upper critical field slope are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.
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Pikul, A. P., N. Caroca-Canales, M. Deppe, P. Gegenwart, J. G. Sereni, C. Geibel, and F. Steglich. "Non-Fermi-liquid behaviour close to the disappearance of ferromagnetism in CePd1-xRhx." Journal of Physics: Condensed Matter 18, no. 42 (2006): L535–L542.
Abstract: The orthorhombic CePd1- xRhx system exhibits a continuous evolution from ferromagnetic order in CePd ( T-C = 6.6 K) to an intermediate-valence ground state in CeRh. Here we report low-temperature ( T >= 0.08 K) specific-heat measurements for concentrations 0.80 <= x <= 0.95 close to the disappearance of magnetic order (similar to 0.87). In contrast to x = 0.8, still demonstrating a smeared phase transition signature at 0.27 K, non-Fermi-liquid behaviour Delta C(T) / T alpha log T is observed in the electronic specific-heat coefficient at x = 0.85. For higher Rh concentrations a weak power-law dependence Delta C(T) / T alpha T-alpha with alpha approximate to 0.4 is found. Upon applying magnetic fields Fermi-liquid-like behaviour Delta C(T) / T similar to const is recovered in all the different samples. The magnetic entropy as well as the concentration of unscreened magnetic moments at 2 K indicate a broad distribution of local T-K values ranging from well below 2 K to far above 50 K.
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Pureur, P., J. G. Sereni, and J. Schaf. "Specific heat and magnetic susceptibility in YNd alloys." Journal of Magnetism and Magnetic Materials 104, no. 3 (1992): 1632–1634.
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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Romero, M. A., A. A. Aligia, J. G. Sereni, and G. Nieva. "Interpretation of experimental results on Kondo systems with crystal field." Journal of Physics: Condensed Matter 26 (2014): 025602. http://dx.doi.org/10.1088/0953-8984/26/2/025602 (accessed September 30, 2023).
Abstract: We present a simple approach to calculate the thermodynamic properties of single Kondo impurities including orbital degeneracy and crystal field effects (CFE) by extending a previous proposal by K. D. Schotte and U. Schotte [Physics Lett. A 55, 38 (1975)]. Comparison with exact solutions for the specific heat of a quartet ground state split into two doublets shows deviations below $10\%$ in absence of CFE and a quantitative agreement for moderate or large CFE. As an application, we fit the measured specific heat of the compounds CeCu$2$Ge$2$, CePd${3}$Si${0.3}$, CePdAl, CePt, Yb$2$Pd$2$Sn and YbCo$2$Zn${20}$. The agreement between theory and experiment is very good or excellent depending on the compound, except at very low temperatures due to the presence of magnetic correlations (not accounted in the model).
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Rus, T., H. Wilhelm, O. Stockert, T. Luhmann, N. Caroca-Canales, J. G. Sereni, C. Geibel, and F. Steglich. "Specific heat of CeIn3-xSnx single crystals in the vicinity of the quantum critical point." PHYSICA B-CONDENSED MATTER 359-361 (2005): 62–64.
Abstract: We report on results of low-temperature specific heat experiments on single crystals of the cubic alloy CeIn3-xSnx (x = 0.55,0.60, 0.65, and 0.80). The measurements support three-dimensional critical spin fluctuations in the vicinity of the magnetic instability, i.e. for x(c) approximate to 0.67, where the antiferromagnetic order vanishes. (c) 2005 Elsevier B.V. All rights reserved.
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Sanchez, R. D., M. T. Causa, J. G. Sereni, M. Vallet-Regi, M. J. Sayaguez, and J. M. Gonzalez-Calbet. "Specific heat, magnetic susceptibility and electrical resistivity measurements on LaNiO3." Journal of Alloys and Compounds 191, no. 2 (1993): 287–289.
Abstract: Measurements of specific heat, magnetic susceptibility and electrical resistivity on LaNiO3 are reported. No evidence of magnetic ordering or metal-insulator transitions is found. From the measured electronic specific heat parameter γ and the Pauli susceptibility χP, a Stoner enhancement parameter is derived. Comparison with band structure calculations performed by other workers is also made.
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Sarkar, R., M. Baenitz, J. G. Sereni, and C. Geibel. "29Si NMR study of the heavy fermion system CeRuSi." Journal of Physics: Conference Series 200 (2010): 012173.
Abstract: A recent investigation of the low temperature properties of the paramagnetic heavy fermion system CeRuSi revealed an anomalous decrease of the coefficient C/T below 6 K, indicating a second low energy scale well below the Kondo temperature of about 50 K. We started an investigation of this unusual behavior using the local probe 29Si-NMR. Here a preliminary 29Si field sweep NMR study in the temperature 4.2-200 K is reported. 29Si-NMR powder spectra obtained at 72.9 MHz could be simulated and shift components 29Kab(T) and 29K c(T) were determined. The shift along the basal plane 29Kab(T) shows the expected behavior with a Curie-Weiss dependence at high T merging in a constant value below 15 K. In contrast the shift along the tetragonal axis reveals an anomalous T dependence below 15 K where 29Kc(T) drops by a factor of 2, confirming the presence of a further low T energy scale. We suspect this drop to be related to the anomalous decrease of C/T below 6 K and discuss possible mechanism. © 2010 IOP Publishing Ltd.
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Sereni, J. G. "Thermomagnetic properties of very heavy fermions suitable for adiabatic demagnetisation refrigeration at low temperature." Philosophical Magazine 100, no. 10 (2020): 1211.
Abstract: With the aim to improve the performance of classical paramagnetic salts for adiabatic refrigeration processes at the sub-Kelvin range, relevant thermodynamic parameters of some new Yb-based intermetallic compounds are analysed and compared. Two main applications are considered: (i) those requiring temperature fixed-points to be reached applying magnetic fields of moderate intensity for satellite applications, and (ii) those which can be used for controlled thermal drifts in laboratory applications. Different thermomagnetic trajectories of the entropy are identified depending on respective specific heat behaviours and the constraints imposed by the Nernst postulate at the sub-Kelvin range. Some simple relationships are proposed to compare the diverse magnetocaloric characteristics of different systems. This procedure allows to include the classical Cerium-Magnesium-Nitride (CMN) salt in that comparison.
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