Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 14: Postersitzung III (Neue u. unkonventionelle Supraleiter, Anwendungen der Supraleitung, Dünne Schichten, JJs und SQUIDs, Schwere Fermionen, Kondo-Systeme)

TT 14.35: Poster

Mittwoch, 26. März 2003, 14:30–19:00, P2c

Magnetic order in CeCu₂(Si_0.5Ge_0.5)₂ studied with magnetic neutron and X-ray scattering — •O. Stockert¹, M. Deppe¹, C. Detlefs², E. Faulhaber³, C. Geibel¹, A. Hiess⁴, D. Hohlwein⁵, A. Kreyßig³, M. Loewenhaupt³, M. Rheinstädter⁴, R. Schneider⁵, A. Schneidewind¹, and F. Steglich¹ — ¹Max-Planck-Institut CPfS, Nöthnitzer Straße 40, D-01187 Dresden — ²European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, France — ³TU Dresden, Institut für Angewandte Physik (IAPD), D-01062 Dresden — ⁴Institut Laue-Langevin, BP 156, F-38042 Grenoble, France — ⁵Hahn-Meitner-Institut, Glienicker Straße 100, D-14109 Berlin

The heavy-fermion system CeCu₂(Si_1−xGe_x)₂ can easily be tuned via alloying from antiferromagnetically ordered CeCu₂Ge₂ to the heavy-fermion superconductor CeCu₂Si₂. The x=0.5 alloy is particulary interesting because it exhibits several phase transistions below the Néel temperature T_N ≈ 3.1 K. In order to determine the magnetic structure and the origin of the different magnetically ordered phases magnetic neutron and X-ray scattering experiments have been performed on the same single crystal at HMI Berlin, ILL Grenoble and ESRF Grenoble.

CeCu₂(Si_0.5Ge_0.5)₂ orders in an incommensurate magnetic structure with a propagation vector τ ≈ (0.275 0.275 0.51) determined by the nesting of the Fermi surface. Two phase transitions within the ordered state can be attributed to a spin reorientation and a lock-in of the magnetic structure. Resonant magnetic X-ray scattering allows to extract information about the moment direction not accessible by neutron diffraction. A model for the magnetic structure will be presented.