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TT: Tiefe Temperaturen

TT 16: Postersitzung II: Amorphe und Tunnelsysteme, Mesoskopische Systeme, Schwere Fermionen, Kernmagnetismus

TT 16.34: Poster

Dienstag, 27. März 2001, 14:30–17:00, Rang S\ 3

Magnetism in UPd_2−xSn — •I. Maksimov¹, S. Süllow¹, F.J. Litterst¹, G.J. Nieuwenhuys², A.A. Menovsky², and J.A. Mydosh² — ¹Institut für Metallphysik und Nukleare Festkörperphysik, TU Braunschweig, Germany — ²Kamerlingh Onnes Lab., Leiden University, The Netherlands

Small deviations from nominal composition in the palladium content of the heavy-fermion compound UPd₂Sn (orthorhombic lattice Pnma) drastically change the physical properties of this material. In particular, instead of an overall metallic resistivity with a positive temperature derivative dρ/dT, UPd_1.85Sn (cubic structure Fm3m) exhibits a negative dρ/dT up to room temperature. Further, while UPd_xSn with x=2 shows a non-magnetic ground state, specific heat and susceptibility of the compound with x=1.85 indicate antiferromagnetic ordering below T_N = 28K. To investigate to what extent chemical pressure or the effect of disorder from Pd deficiency causes the non-metallic resitivity, we have studied compounds UPd_xSn with x=1.95 (Pnma) and 1.9 (Fm3m). The first shows properties very similar to UPd₂Sn, while the latter resembles the behavior of UPd_1.85Sn, indicating that the physics of these compounds is mainly governed by bandstructure effects accompanying the structural transition.
Supported by DFG under grant no. SU 229/1-1.