Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 17: Heavy Fermions

TT 17.3: Vortrag

Mittwoch, 28. März 2007, 14:30–14:45, H18

Polarization dependent Ce-M₄₅ x-ray spectroscopy on CeCu₂Si₂ and CePd₂Si₂: a new approach to determine the symmetry of the lowest crystal field states — •P. Hansmann¹, A. Severing¹, Z. Hu¹, C.F. Chang¹, S. Klein¹, H.J. Lin², C.T. Chen², B. Fak³, C. Geibel⁴, F. Steglich⁴, and L.H. Tjeng¹ — ¹II. Phys. Inst., Univ. Köln, Cologne — ²NSRRC Hsinchu, Taiwan — ³CEA, SPSMS, Grenoble, France — ⁴MPI CPFS, Dresden

In the past neutron scattering as the standard technique has given confusing and often contrary results about the symmetry of the lowest crystal field states of correlated RE compounds, particularly on CeCu₂Si₂ [1,2] and CePd₂Si₂ [3,4,5]. The knowledge about these lowest states is crucial for the understanding of the magnetic properties and also provides an important ansatz for a proper description of the low energy electronic structure including the Fermi surface. We will present results obtained with a different technique, namely soft-x-ray absorption spectroscopy (XAS) at the Ce-M₄₅ edges. This technique is known to be sensitive to the symmetry of the initial state and through the polarization dependence we obtain direct spectroscopic information about the |J_z⟩ admixtures of the ground state. XAS used in this manner should be a powerful new tool, complementary to neutrons, in determining the symmetry of crystal field ground states in RE.

[1] S. Horn et al. PRB 23 (1981) 3171 [2] E.A. Gorimychkin et al. PRB 47 (1993) 14280 [3] A. Severing et al. PRB 39 (1989) 2557 [4] R.A. Steemann et al. J. Appl. Phys. 67 (1990) 5203 [5] N.H. van Dijk et al. PRB 61 (2000) 8922