Regensburg 2002 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 21: Schwere Fermionen, Kondo-Systeme II (gemeinsam mit FV-Magnetismus)

TT 21.6: Vortrag

Donnerstag, 14. März 2002, 15:45–16:00, H20

Neutron study of the magnetic order in CeCu2(Si1−xGex)2 with low Ge-content — •M. Deppe1, R. Borth1, J. Custers1, C. Geibel1, P. Hinze1, D. Hohlwein2, E. Lengyl1, N. Oeschler1, R. Schneider2, O. Stockert1, H. Q. Yuan1, and F. Steglich11MPI-CPfS, Noethnitzer Str. 40, 01187 Dresden — 2HMI, Glienicker Str. 100, 14109 Berlin

Studies on polycrystalline samples of the heavy-fermion alloy CeCu2(Si1−xGex)2 showed that the system can be tuned from an antiferromagnetically ordered Ce-compound at x=1 to a heavy-fermion superconductor at x=0. However, no magnetic Bragg peaks could be observed with neutron scattering for low Ge concentration x<0.6 . Since the nature of the magnetic order in pure CeCu2Si2 is still a matter of debate, and since it is suggested to be strongly connected with the superconducting state, a more precise knowledge of the evolution of the magnetic order in this alloy is crucial for obtaining a deeper understanding of the magnetism and superconductivity in pure CeCu2Si2. We have therefore grown large single crystals of CeCu2(Si1−xGex)2 which allowed us to perform neutron diffraction using the flat-cone diffractometer E2 at the HMI, Berlin. We observed magnetic reflections and could determine the propagation vector of the antiferromagnetic order for Ge concentrations down to x=0.05. We will compare our results with thermodynamic measurements and the phase diagram established for the single-crystals. The experimental evidences for an antiferromagnetic ordering with very low moments will be discussed in the context of theoretical calculations.

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