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TT: Tiefe Temperaturen

TT 30: Postersitzung IV: Kritische Ph
änomene, Quantenstörstellen, niederdimensionale Systeme

TT 30.4: Poster

Thursday, March 11, 2004, 14:30–19:00, Poster A

Magnetic response of the non-Fermi-liquid YbRh₂Si₂ — •O. Stockert¹, N. Bernhoeft², M. Koza³, J. Ferstl¹, A. Murani³, C. Geibel¹, and F. Steglich¹ — ¹Max-Planck-Institut CPfS, Nöthnitzer Straße 40, D-01187 Dresden — ²CEA Grenoble, DRFMC, F-38054 Grenoble, France — ³Institut Laue-Langevin, BP 156, F-38042 Grenoble, France

Deviations from the usual Landau-Fermi-liquid theory are observed in an increasing number of correlated electron system which are close to a magnetic instability where a transition from a nonmagnetic ground state to a magnetically ordered state occurs. YbRh₂Si₂ is the first Yb-based compound which obeys non-Fermi-liquid behavior as seen in unusual temperature dependences of thermodynamic and transport properties at temperatures above the very low ordering temperature T_N = 65 mK. In the vicinity of the magnetic instability in YbRh₂Si₂ one expects critical spin fluctuations which are the origin of the non-Fermi-liquid behavior. Inelastic neutron scattering on YbRh₂Si₂ powder has been performed to investigate the magnetic response. The high energy response is dominated by crystalline electric field excitations, found at ≈ 27, and 42 meV. In contrast, the low energy response is quasielastic and shows a critical slowing down as the temperature is reduced. However, the quasielastic response seems to be non-Lorentzian like, but could be fitted by a phenomenological model for the susceptibility using a distribution of relaxation rates with an upper, temperature independent bound and a lower bound varying roughly linearly with T.