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TT: Tiefe Temperaturen

TT 25: Correlated Electrons - Poster Session

TT 25.80: Poster

Mittwoch, 29. März 2006, 14:30–18:30, P1

High temperature specific heat and crystal field of the non-Fermi-Liquid system YbRh₂Si₂ — •J. Ferstl, C. Geibel, O. Stockert, and F. Steglich — Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany

The heavy fermion system YbRh₂Si₂ has attracted considerably interest in the last years, being located very close to a quantum critical point (QCP). Strong Kondo-like fluctuations lead to a very weak magnetic order with a transition temperature of only T_N = 70 mK at ambient pressure. A lot of physical investigations were done in the low temperature region, but much less investigations and analysis were devoted to the behaviour at higher temperatures. We shall present measurements of the specific heat C_p at higher temperatures. The results are analysed in view of crystal field (CEF) effects and discussed in comparison with results from inelastic neutron scattering. C_p of YbRh₂Si₂ and LuRh₂Si₂ were measured in the temperature range 2 K ≤ T ≤ 300 K. From the difference we deduced the contribution C_4f of the Yb-4f-electrons. We confirm the presence of a broad maximum between 40 K and 80 K in C_4f. This maximum can be related to the first excited CEF level which, according to neutron data, is located around 17 meV. While C_4f is more conclusive than neutron data for this lowest excited CEF level, C_4f(T) is less conclusive for the higher levels, for which neutron data gave rather precise excitation energies of 25 meV and 43 meV. Thus the combination of specific heat and neutron data allows a more reliable determination of the whole CEF scheme.