IOP PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER J. Phys.: Condens. Matter 20 (2008) 025201 (8pp) doi:10.1088/0953-8984/20/02/025201 Electronic structure of CeRhSn 2 and LaRhSn 2 from x-ray photoemission spectroscopy and band structure calculations M Gam˙ za 1 ,A ´ Slebarski 1 and H Rosner 2 1 Institute of Physics, University of Silesia, 40-007 Katowice, Poland 2 Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany E-mail: andrzej.slebarski@us.edu.pl and rosner@cpfs.mpg.de Received 1 August 2007, in final form 1 October 2007 Published 6 December 2007 Online at stacks.iop.org/JPhysCM/20/025201 Abstract We report on the electronic structure and magnetic properties of the Kondo lattice system CeRhSn 2 and of the reference compound LaRhSn 2 . The Ce 3d and 4d x-ray photoemission spectroscopy (XPS) data point to a stable configuration of the Ce 4f shell in CeRhSn 2 . The ac magnetic susceptibility measurements reveal two magnetic transitions for CeRhSn 2 at temperatures T C1 ≈ 4 K and T C2 ≈ 3 K. The temperature dependences of the ac susceptibility show also broad maxima at about 17 and 15 K for CeRhSn 2 and LaRhSn 2 , respectively. Such features hint at spin fluctuations on Rh atoms. To get detailed insight into the electronic structure of both CeRhSn 2 and LaRhSn 2 we perform ab initio band structure calculations within the local (spin) density approximation (L(S)DA) and using the LSDA + U approach to account for the strong Coulomb interactions within the Ce 4f shell. The LSDA + U approximation gives qualitatively the correct physical picture of Ce 3+ in CeRhSn 2 . The reliability of the theoretical results is confirmed by the comparison of the calculated XPS valence band spectra with experimental data. A Fermi surface analysis shows that there are some parallel sections of the sheets, which could generate ‘nesting’ instabilities. These nesting features might be responsible for the spin fluctuations suggested by the ac susceptibility measurements. (Some figures in this article are in colour only in the electronic version) 1. Introduction Many Ce-based intermetallics exhibit a variety of unusual ground states, including complex magnetic structures, heavy fermion states (both normal and superconducting), magnetic Kondo lattices with reduced magnetic moments or non- magnetic insulating Kondo lattices. The reason for such a diversity of physical phenomena is a delicate interplay between two competing mechanisms: the local on-site Kondo screening of the localized Ce moments and the long range Ruderman– Kittel–Kasuya–Yosida (RKKY) interactions. The first effect suppresses the Ce 4f magnetic moments and may lead to the Abrikosov–Suhl resonance manifesting itself as the narrow peak in a quasi-particle density of states (DOS) near the Fermi level, while the latter one may lead to long range magnetic order of the localized Ce moments. Finally, the stability of different ground states depends strongly on the on- site hybridization strength between the 4f electrons and the conduction band, the bare f level position in the conduction band, the number of electrons occupying the f shell and the magnitude of on-site Coulomb interaction within this shell. The full understanding, however, of the relation between band structure and the ground state properties in Ce-based intermetallics still requires much further investigation. Over the past few years, much attention has been devoted to magnetically ordered Kondo lattice compounds. Some of them were found to undergo a superconducting transition with applied pressure via a heavy fermion state [1–4]. The magnetic interactions are believed to play an essential role in the formation of the Cooper pairs in this superconducting state. 0953-8984/08/025201+08$30.00 © 2008 IOP Publishing Ltd Printed in the UK 1