Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The valence-fluctuating Eu systems EuX2Si2, with X being the transition metal Co, Ir, or Rh, show different types of ground states, strongly depending on X. The instability of the Eu 4f shell underlies this phenomenon and leads among other effects to different valence states ranging from Eu2+ over mixed valence and intermediate valence behavior to Eu3+ [1]. Investigations on the structure and the magnetic behavior of EuCo2Si2, EuIr2Si2, and EuRh2Si2 have revealed their Eu valence. Further experiments on specific heat and resistivity gave insights to magnetic ordering, electronic correlations, and possible valence fluctuations. We report about a systematic de Haas-van Alphen study on the Fermi-surface development of the EuX2Si2 compounds in magnetic fields up to 35 T. High-quality single crystals were available for the first time. We will focus on the Fermi-surface topology obtained by angle dependent measurements and discuss a comparison to band-structure calculations .