Regensburg 2002 – scientific programme

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TT: Tiefe Temperaturen

TT 3: Schwere Fermionen, Kondo-Systeme I

TT 3.4: Talk

Monday, March 11, 2002, 10:15–10:30, H18

Gap formation in the semimetal U₂Ru₂Sn : evidence from ¹¹⁹ Sn NMR investigations — •M. Baenitz¹, A. Rabis¹, S. Paschen¹, V.H. Tran¹, N. Senthilkumaran¹, F. Steglich¹, P. de V. duPlessis², and A.M. Strydom³ — ¹MPI für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, D - 01187 Dresden — ²Department of Physics, University of the Witwatersrand PO Wits 250, Johannesburg, South Africa — ³Department of Physics, Rand Afrikaans University, PO 524, Johannesburg, South Africa

We report measurements of the ¹¹⁹Sn nuclear spin - lattice relaxation rate 1/T₁ and the Knight shift K for U₂Ru₂Sn as a function of temperature. The T dependence of 1/T₁ is very similar to that of CeNiSn with the only difference that the temperature scale is increased roughly by a factor of 10. Therefore a first estimate gives a gap value of Δ / k_B≈ 140 K ( ≈ 14 K for CeNiSn). At low temperatures similar to CeNiSn a T₁T=constant behaviour is observed which indicates the presence of residual density of states at the Fermi level N(E_F) in the pseudo-gap. Furthermore measurements on the ¹¹⁹Sn Knight shift, the susceptibility, the specific heat, the electrical resistivity and the Hall coefficient are discussed in the context of a gap formation due to correlations in this semimetal. Investigations on the non-magnetic reference compound Th₂Ru₂Sn are also presented.