Electronic structure and transport properties of CeNi9In2

Abstract

We investigated CeNi 9 In 2 compound, which has been considered as a mixed valence (MV) system. Electrical resistivity vs. temperature variation was analysed in terms of the model proposed by Freimuth for systems with unstable 4f shell. At low temperature the resistivity dependence is consistent with a Fermi liquid state with a contribution characteristic of electron-phonon interaction. Ultraviolet photoemission spectroscopy (UPS) studies of the valence band did not reveal a Kondo peak down to 14 K. A difference of the spectra obtained with photon energies of low and high photoionization cross sections for Ce 4f electrons indicated that 4f states are located mainly close to the Fermi energy. The peaks related to f 5/2 1 and f 7/2 1 final states cannot be resolved but form a plateau between -0.3 eV and the Fermi energy. X-ray photoemission spectroscopy (XPS) studies were realized for the cerium 3d level. The analysis of XPS spectra within the Gunnarsson-Shönhammer theory yielded a hybridization parameter of 104 meV and non-integer f level occupation, being close to 3. Calculations of partial densities of states were realized by a full potential local orbital (FPLO) method. They confirm that the valence band is dominated by Ni 3d states and are in general agreement with the experiment except for the behavior of f-electrons.

Kondo lattice behavior observed in the CeCu9In2 compound

“…The first one is located below E F , while the second one is placed above the Fermi level. Similar situation was observed previously in case of the CeNi 9 In 2 compound [9]. Discrepancy between theoretical and experimental value of Sommerfeld coefficient of CeCu 9 In 2 is not startling for us and it testifies presence of strong correlations in this compound.…”

“…Moreover, polycrystalline samples obtained by arc-melting may exhibit certain disorder in particular at the surface, which can supress spectral intensity at E F . It is also worth to compare spectra presented here for CeCu 9 In 2 , with those reported previously for CeNi 9 In 2 [9]. In case of the compound with Ni, the Ni 3d states are located almost at the Fermi level and interact strongly with f states resulting in the mixed valence state.…”

“…This fact was interpreted as a symptom of a Pauli paramagnetism [6]. It should be mentioned that replacement of a transition metal may have a significant effect; recently, a mixed valence state has been proposed for the isostructural CeNi 9 In 2 compound [3,7,8,9].…”

Law and Disorder: Special Stacking Units—Building the Intergrowth Ce6Co5Ge16

“…Furthermore, the Ce 3d 5/2 state can be fitted to two peaks at 881.4 and 885.2 eV which are assigned to the v 0 and v ′ states of Ce 3+ , respectively. , Similarly, the Ce 3d 3/2 state can be fit to 899.9 and 903.5 eV which are assigned to the u 0 and u ′ states of Ce 3+ , respectively. No evidence of Ce in the 4+ oxidation state is observed. , The Co 2p photoelectron spectrum indicates that the Co present is primarily as Co (0) (2p 3/2 : 778.8 eV; 2p 1/2 : 792.8 eV) . The data also show that there is a small amount of Co present in a higher oxidation state, a mixed Co 2+ and Co 3+ state. − Finally, we note that there is a small amount of Sn present in the sample even after extensive sputtering using an Ar GCIB.…”

“…No evidence of Ce in the 4+ oxidation state is observed. 25,26 The Co 2p photoelectron spectrum indicates that the Co present is primarily as Co (0) (2p 3/2 : 778.8 eV; 2p 1/2 : 792.8 eV). 27 The data also show that there is a small amount of Co present in a higher oxidation state, a mixed Co 2+ and Co 3+ state.…”