Renormalized electronic structures of CeSi2, CeRu2 and CeAl2 (original) (raw)
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Spectroscopic evidence of configuration-dependent hybridization in a cerium compound: CeRh3
Zeitschrift für Physik B Condensed Matter
Evidence is given for a configuration dependent hybridization in the spectroscopy of a strongly hybridized compound like CeRh 3. This is achieved by comparing the results of 4f inverse photoemission and Ce 3d core level spectroscopies to the predictions of the single impurity Anderson model (SIAM). This analysis shows that the SIAM is not able to quantitatively describe, within a single set of parameters, the results of both spectroscopies. A considerably better agreement with experiments is instead obtained when changes in the hybridization parameter are allowed in the different final states. This result suggests that the hybridization between f and band states strongly depends on the 4f configuration as theoretically predicted.
Physical Review B, 2012
We have determined the ground-state wave functions and crystal-field-level schemes of CeRh 2 Si 2 and CeRu 2 Si 2 using linear polarized soft x-ray-absorption spectroscopy (XAS) and inelastic neutron scattering. We find large crystal-field splittings and ground-state wave functions which are made of mainly J z = |±5/2 with some amount of |∓3/2 in both the compounds. The 4f 0 contribution to the ground state of several members of the CeM 2 Si 2 family with M = (Cu, Ru, Rh, Pd, and Au) has been determined with XAS, and the comparison reveals a trend concerning the delocalization of the f electrons. Absolute numbers are extracted from scaling to results from hard x-ray photoelectron spectroscopy on CeRu 2 Si 2 by Yano et al.
Review on cerium intermetallic compounds: A bird's eye outlook through DFT
Progress in Solid State Chemistry, 2013
Cerium based intermetallic compounds exhibit a wealth of physical properties originating from the electronic states of Ce, i.e. diamagnetic Ce 4þ ([Xe] 4f 0), paramagnetic Ce 3þ ([Xe] 4f 1). Switching between the electronic states can be induced either chemically such as by inserting hydrogen, by substitutions (size effects) or physically by applying external pressure. The review exposes different classes of Ce intermetallic compounds whose properties are interpreted and/or predicted thanks to quantum computations in the framework of the density functional theoretical (DFT). Focus is broadly made on the family of the equiatomic cerium intermetallic compounds, namely ternary CeTX where T is a transition metal and X a p-element where the hydrogenation effects take a considerable place in changing the electronic configuration of Ce. Other stoichiometries of cerium intermetallic compounds with their physical properties are discussed subsequently in the later part of the review. Rather than presenting an exhaustive enumeration of stoichiometries, illustrative case studies are selected for each class of materials to provide, after presenting the experimental context, insights into original outcome from methods targeted at selective physical and chemical properties.
Temperature dependence of high-resolution resonant photoemission spectra of CeSi
Journal of Electron Spectroscopy and Related Phenomena, 2005
High-resolution Ce 4d-4f resonant photoemission spectra near the Fermi level of CeSi with the Néel temperature of 5.9 K have been measured at temperatures from 5.6 to 200 K, in order to investigate the competition between the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction and the Kondo effect. As temperature is decreasing down to 30 K, the intensity due to the Ce 4f 1 5/2 final state increases because of the evolution of the heavy Fermion behaviour caused by the Kondo effect. The intensity, however, decreases gradually from 30 to 5.6 K. This indicates that the heavy Fermion behaviour is strongly suppressed by the anti-ferromagnetic ordering due to the RKKY interaction.
Structure, force fields, and vibrational spectra of cerium tetrahalides
Journal of Structural Chemistry, 2008
The geometrical structure, force fields, and vibrational spectra of CeX 4 (X = F, Cl, Br, I) were investigated by second, third, and fourth order Möller-Plesset perturbation theory, CISD+Q configuration interaction method, and the CCSD(T) coupled cluster method. Calculations on CeF 4 were also performed by multiconfiguration second order perturbation theory MCQDPT2/CASSCF. The wave function of the ground state of CeX 4 molecules was found to be appreciably non-one-configurational; this property increases from cerium fluorides to iodides and leads to the divergence of the series of Möller-Plesset perturbation theory. The calculated data point to a tetrahedral equilibrium nuclear configuration in CeX 4 molecules. The energy barriers to the inversion of the tetrahedral CeX 4 molecules via the square configurations are high enough, 74-89 kJ/mol. The calculated vibration frequencies, effective internuclear distances, and mean amplitudes of nuclear vibrations in CeF 4 agree with IR and Raman spectroscopic and high-temperature gas-phase electron diffraction data.
Changes in the electronic structure of cerium due to variations in close packing
Physical Review B, 2004
Here we use electron energy-loss spectroscopy in a monochromated transmission electron microscope with 100 meV energy resolution and 2 Å spatial resolution to show that the electronic structure of face centered cubic ␥ and double hexagonal close-packed  cerium are considerably different, contrary to previous assumptions in literature. These results are supported by synchrotron-radiation-based x-ray absorption, multielectronic atomic spectral simulations, and local density approximation calculations, illustrating that changes in ͕111͖ stacking sequences can drive substantial electronic changes in close-packed phases of cerium that have a similar atomic volume.
Mixed valence state of Ce ions in CeNi2Al3
Journal of Alloys and Compounds, 2001
X-ray photoelectron spectroscopy (XPS) and magnetic susceptibility (x) of CeNi Al and of the reference compound YNi Al are 2 3 2 3 reported. Both valence band and core level spectra were analyzed. The x(T ) curve of CeNi Al shows a maximum around 22 K, 2 3 characteristic for the intermediate valence state of Ce ions, and at high temperatures obeys a Curie-Weiss law with an effective magnetic moment m 52.48 m / f.u. The Ce 3d and 4d XPS spectra have confirmed the mixed valence state of Ce ions in CeNi Al . The f eff B 2 3 occupancy n , and coupling D between the f level and the conduction states are derived to be about 0.85 and 80 meV, respectively.
Effects of electronic correlation in CeRuAl compound
Applied Physics A, 2022
Pioneering of condensed matter physics relates to various factors of electronic correlations. Exploring new materials, always achieve important roles to develop the understanding of magnetism in correlated matter. Rare-earth-based compounds especially Cerium-based inter-metallics display different types of interesting properties and the reason behind these fascinating properties is the strongly correlated nature of these materials. In broadening our level of understanding on correlated materials especially on low temperatures, we aim to set a report on the compound of CeRuAl. Physical properties (magnetic, transport and electronic) of CeRuAl are measured for the temperature ranges 400 K to 0.5 K and in the magnetic field up to 7 T. It is observed that the Sommerfeld coefficient, which is calculated from the measurements of heat capacity, has the value of γ = 62 mJ/mol K 2. At temperature 1.1 K, this compound CeRuAl shows mixed valent behavior. At the lower temperature range (0.9 K to 0.4 K) with applied field up to 0.5 T, the superconductivity property is evident. Absence of quick rise in low-temperature resistivity indicates that the gap formation in the electronic density of states does not exist.
CeCu2Si2: Renormalized band structure, quasiparticles and co-operative phenomena
Physica B: Condensed Matter, 1993
The prototype heavy fermion compound CeCu2Si 2 exhibits a rather complicated phase diagram at low temperatures. Recently, a number of phase transitions at temperatures above the superconducting T c were discovered. These transitions seem to be correlated with the appearance of superconductivity. We calculate the quasiparticles in CeCuESi 2 by means of the renormalized band structure method. The results for the Fermi surface suggest that the new phase transition may be driven by a topological transition in the system of the heavy quasiparticles.
Quantitative line shape analysis of the Kondo resonance of cerium compounds
Physica B-condensed Matter, 2002
By use of high-resolution photoelectron spectroscopy we investigate the 4f spectral function of the heavy fermion compound CeRu2Si2 in the energy range close to the Fermi level. A normalization method proposed by Greber et al. (Phys. Rev. Lett. 79 (22) (1997) 4465) allows to resolve the Kondo resonance and its crystal field satellites. We discuss the applicability of this method with respect to a quantitative analysis of the data, and compare our experimental results to non-crossing approximation (NCA) calculations in the frame of the single impurity Andersson model (SIAM).