Sereni, J. G. "Characteristic concentrations in Ce ground state transformations induced by alloying." PHYSICA B 215, no. 4 (1995): 273–285.
Abstract: The evolution of magnetic, transport, thermal, structural and spectroscopic properties as a function of the Ce-ligand substitution, Ce(X(1-x)Y(x))(k)Z(l), is analyzed on about 30 systems. Two concentrations, x(0) and x(cr), related to independent transformations of the Ce ground state (GS) are characterized: x(0) corresponds to the magnetic phase boundary and x(cr) to a change of regime in the x dependence of all the aforementioned properties. The usual qualitative comparison of different Ce systems, made according to Doniach's model (that takes the x(0) concentration as reference), is improved by the possibility of a quantitative comparison among those systems by normalizing the Ce-ligand concentrations as Y = (X – X(cr))/(X(0) – X(cr)). The microscopic origin of x(cr) is found to be related to the modification of the Ce-GS symmetry properties when the increase of the hybridization strength becomes comparable to the crystal field splitting and, therefore, ground and excited crystal held states overlap. Intrinsic differences between heavy fermion and intermediate valence GS, their coexistence with magnetic order and the formation of non-Fermi liquid states are discussed in terms of the relative values of x(0) and x(cr).
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SERENI, J. G. "SYSTEMATICS ON THE CERIUM MAGNETIC-TRANSFORMATIONS INDUCED BY ALLOYING." JOURNAL OF ALLOYS AND COMPOUNDS 207 (1994): 229–236.
Abstract: A systematic study on the competition between on-site and inter-site magnetic interactions is performed on Ce intermetallics through magnetic, thermal, transport, structural and spectroscopic measurements analyses. It is shown that the volume and the electronic concentration variation produced by alloying the Ce-ligand, are not equivalent and only the volume reduction. produces the maximum in the ordering temperature predicted by theory. For the magnetic to intermediate valence transformations, a change of regime is observed at a critical Ce-ligand substitution, which corresponds to a change in the substitution dependence of the experimental parameters. On the contrary, no change of regime is detected for the magnetic to heavy fermion transformation. The different regimes are correlated with the respective hybridization strengths of the ground and excited crystalline field states through the temperature dependence of the electrical resistivity. Such a correlation allows us to draw a generalized phase diagram containing these types of transformation.
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Sereni, J. G. "Chapter 98 Low-temperature behaviour of cerium compounds: Specific heat of binary and related intermetallics.", edited by J. and L. R. E. Karl A. Gschneidner, 1–59. Vol. Volume 15. Elsevier, 1991.
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Sereni, J. G. "Correlation between atomic spacing and magnetic behavíour in Ce binary compounds." Revista Brasileira de Física 21, no. 2 (1991): 280–289.
Abstract: The magnetic behaviour of 80 Ce-binary compounds is correlated with the minimum Ce-Ce spacing (D) in the lattice. Among the magnetically ordered compounds, three regions can be defined: I) with D smaller than the trivalent Ce diameter, where all the compounds order antiferromagnetically, with fractional entropy and large values of γ and θp. II) With 3.7amgstron < D < 4.1amgstron, which includes the ferromagnetic compounds, and III) with D > 4.1amgstron, where most of the compounds order antiferromagnetically with full entropy. The compounds which do not order magnetically (region IV) are distributed in two ranges of energy: < 10K for the heavy fermions and > 100K for the intermediate valent ones. Spin fluctuation effects are observed in the compounds with large D values and small volume contraction.
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SERENI, J. G. "The role of “p-like†orbitals in Ce valence instabilities." Journal of Magnetism and Magnetic Materials 47-48, no. FEB (1985): 228–230.
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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Sereni, J. G. "Rare earth metal melting-temperature anomalies." Journal of Physics and Chemistry of Solids 45, no. 11-12 (1984): 1219–1223.
Abstract: The bond strength weakening, responsible for the melting temperature (Tƒ) anomalies in some rare earths elements (RE), is studied through their enthalpies of fusion (ΔHƒ). Different electronic configurations are recognized through the Engel correlations, and their contribution to ΔHƒare evaluated following Gschneidner's criterion. Non-integral valent RE are discussed in detail. Their anomalously low Tƒ value is related to bond strength weakening due to p-f hybridization. The Richard-Tamman value for the entropy of fusion (ΔSƒ = ΔHƒ/Tƒ = 2.3 eu) is verified for the calculated ΔHƒ and the measured Tƒ ratio.
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Sereni, J. G. "The effect of the electronic and structural environment on the valence of cerium." Journal of the Less Common Metals 86, no. 2 (1982): 287–298.
Abstract: By means of a semiempirical analysis the electrostatic energy Eψ of a charge immersed in the screened Coulomb potential of the total charge distribution of the metal was selected as the most appropriate parameter for correlating different cerium environments. The choice was made by determining the smallest dispersion in plots of various physicochemical parameters versus the rate of depression α of the superconducting transition temperature Tc of thorium-based alloys containing cerium impurities. The magnetic moment of cerium, which depends on the environment, was found to have the greatest effect on the depression of Tc. Eψ was found to be proportional to .
The analysis was extended to some ABj compounds (A ≡ elements of groups II–V including cerium and thorium; Bj ≡ N, Sn3, Tl3, Rh3, Co2, Ir2, B6 and Be13). An empirical relationship between Eψ and the volume contraction due to the formation of the compound was found. The cerium valence for any CeBj compound is deduced from the Eψ(Ce) value compatible with the curve of versusEψ(A), taking into account the fact that the valence and atomic radius of cerium are related.
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SERENI, J. G. "THE CERIUM METALLIC RADIUS IN AB2 (C15) LAVES COMPOUNDS (A=CE)." JOURNAL OF THE LESS-COMMON METALS 84, no. 1 (1982): 1–10.
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Sereni, J. G. "Evaluation of the cerium metallic radius in its AB2 laves phases." In Proceedings International Conference on Valence Fluctuations in Solids, edited by L. M. Falicov, W. Hanke and M. B. Mapple, 409. North-Holland Publishing Company, 1981.
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Sereni, J. G. "Evidence for valence fluctuation in the CeSn3 compound." Journal of Physics F: Metal Physics 10, no. 12 (1980): 2831–2840.
Abstract: Presents the experimental results of magnetisation, magnetic susceptibility (at normal pressure and under a pressure of 6 kbar), electrical resistivity and thermal expansion performed on a single sample of CeSn3. These measurements were done over the temperature range of 1.4<T<300K. The author used an extension of the Ramirez-Falicov theory outlined by Alascio et al. (1972, 1973) to show that these and previous specific heat and thermopower results can be related by including a mixing between the two possible Ce configurations.
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