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Kappler, J. P., E. Beaurepaire, G. Krill, C. Godart, G. Nieva, and J. G. Sereni. "Magnetic to non-magnetic transition of Ce induced by volume in Ce(Pd, Ni) and electron concentration in Ce(Pd, Rh)." Journal de Physique Colloques 49, no. C-8 (1988): 723–724.
Abstract: Unit cell volume, magnetic properties and LIII X-ray absorption edge studies in Ce(Pd, M) with M = Ni or Rh show that the Ce demagnetization is mainly driven by volume reduction in Ce(Pd, Ni) and essentially due to the reduction of the d electron number in Ce(Pd, Rh).
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Kappler, J. P., E. Beaurepaire, G. Krill, J. G. Sereni, C. Godart, and G. L. Olcese. "Anomalous behaviour of X-ray absorption observed on the highly correlated cerium nitride (CeN) compound." Journal de Physique I 1 (1991): 1381–1387.
Abstract: In this study, we present recent X-ray Absorption Spectroscopy (XAS) results obtained on highly pure cerium nitride (CeN) compounds. CeN is the “archetype” of the strongly mixed-valent (MV) cerium compounds, where the ground state properties are governed by strong hybridization effects between the 4f and the conduction electrons. We will show that, in clear contradistinction with earlier results, the L ${\rm III,II}$ absorption edges of cerium in CEN do not exhibit the two contributions usually observed in strong MV systems. Indeed, in all cases only one single white line is observed. This anomalous behaviour is related with similar results obtained recently on in-situ prepared CeN studied by both L ${\rm III}$ absorption and Ce 2p X-ray photoemission (XPS). The possible influence of the presence of p conduction states to explain this anomalous behaviour is addressed.
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Kappler, J. P., M. J. Besnus, E. Beaurepaire, A. Meyer, J. Sereni, and G. Nieva. "Magnetic transition in the CePd3Bx system." Journal of Magnetism and Magnetic Materials 47 (1985): 111–114.
Abstract: Susceptibility, high-field magnetisation, resistivity and heat capacity data for the CePd3Bx system are reported. The observed valence transition of Ce is the first example of a transition from an IV state system to a stable magnetic 4f1 state system, whose properties are tentatively ascribed to an aleatory cooperative state, due to the inhomogeneous character of the valence transition, rather than to a Kondo effect.
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SERENI, J. G., E. BEAUREPAIRE, and J. P. KAPPLER. "EFFECTS OF VOLUME AND ELECTRONIC CONCENTRATION ON THE CE(PD1-XMX) COMPOUNDS (M=NI, RH, AND AG)." PHYSICAL REVIEW B 48, no. 6 (1993): 3747–3754.
Abstract: High-field-magnetization, magnetic-susceptibility, specific-heat, electrical-resistivity, lattice-parameter, L(III) x-ray absorption spectroscopy, and x-ray-absorption near-edge spectroscopy measurements are discussed for Ce(Pd1-xMx) (M = Ni, Rh, and Ag) pseudoternary alloys. The Pd substitution by a holelike metal (Ni and Rh) induces the demagnetization of the Ce atom by two different mechanisms: electronic concentration variation (DELTAZ, for M = Rh) and volume reduction (DELTAV, for M = Ni). The Pd substitution by an electronlike metal (Ag) induces drastic changes in the magnetic structure with only a 2 at. % impurity. The experimental results indicate: (i) a continuous transformation from a ferromagnetic (F) to a nonmagnetic (NM) ground state induced by the DELTAZ variation and (ii) a drastic transformation from F to NM, by the DELTAV change at a certain critical concentration. The ferromagnetic-to-antiferromagnetic transition induced by Ag is described as due to the variation of the charge screening at the nonmagnetic site.
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SERENI, J. G., O. TROVARELLI, A. HERR, J. P. SCHILLE, E. BEAUREPAIRE, and J. P. KAPPLER. "On the edge of tetravalent Ce in CePd7." Journal of Physics: Condensed Matter 5, no. 18 (1993): 2927–2934.
Abstract: Data on the magnetic susceptibility, low-temperature specific heat and x-ray absorption spectroscopy (Ce L(III) and M(IV,V) edges) for CePd7 and its reference compound YPd7 are presented. The respective Pauli susceptibilities chi0 of 0.11 x 10(-3) emu mol-1 and 0.50 x 10(-3) emu mol-1 and the respective Sommerfeld coefficients gamma of 9.8 mJ K-2 mol-1 and 35.8 mJ K-2 mol-1 are much smaller (per atom) than those of the corresponding components (Ce, Y and Pd). The valence extracted from the Ce L(III) edge is 3.5. The chi0/gamma-ratios are found to be 0.012 emu K2 J-1 and 0.014 emu K2 J-1 for CePd7 and YPd7, respectively. Such a value for CePd7 corresponds to that of a free-electron system instead of an intermediate-valence system (0.035 emu K2 j-1).
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