Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 6: Correlated Electrons: Heavy Fermions

TT 6.1: Vortrag

Montag, 25. Februar 2008, 09:30–09:45, EB 202

Crystal-field ground states of CeX₂Si₂ (X= Cu, Ru, Rh,Pd, and Au) determined by linear polarized soft x-ray absorptionat the Ce M_4,5 edges — •T. Willers¹, A. Severing¹, C.-F. Chang¹, P. Hansmann¹, M.W. Haverkort¹, N. Hollmann¹, Z. Hu¹, H.J. Lin², C.T. Chen², H. Aoki³, E. Bauer⁴, C. Geibel⁵, P. Lejay⁶, and L.H. Tjeng¹ — ¹Institute of Physics II, University of Cologne,Germany — ²National Synchrotron Radiation ResearchCenter, Taiwan — ³Center for Low TemperaturePhysics, Tohoku University, Sendai, Japan — ⁴LosAlamos National Laboratory, NM, USA — ⁵MPI fürChem. Physik fester Stoffe, Dresden, Germany — ⁶Institut Néel, CNRS, Grenoble, France

Knowledge of the spatial distribution of the 4f wave function in rare-earth Heavy-Fermion systems forms one of the basic ingredients for the modelling of their unusual and exotic properties. In the past, neutron scattering as the standard technique to determine the crystal-field scheme has often given contradicting results Here we use an alternative method. We have recently shown that polarization dependent soft-x-ray absorption spectroscopy is a powerful tool to probe the charge distribution of the crystal-field ground state of Ce ions. Through the polarization dependence we obtain direct spectroscopic information about the various Jz admixtures of the ground state. The so-called linear dichroic signal at the Ce M_4,5 edges can be very large and is easily measured, thereby providing accurate quantitative information. A systematic investigation of the 4f ground state wave function will be presented for the CeX₂Si₂ series (X=Cu, Ru, Rh, Pd, Au).