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Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 3: Correlated Electrons - Heavy Fermions

TT 3.7: Talk

Friday, March 4, 2005, 11:45–12:00, TU H3027

Magnetic field-induced non-Fermi-liquid resistivity in YbAgGe single crystals — •Philipp G. Niklowitz1, Georg Knebel1, Sergey L. Budko2, Paul C. Canfield2, and Jacques Flouquet11SPSMS/CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 9, France — 2Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA

Hexagonal YbAgGe has recently been recognised as a new heavy-fermion (HF) system with TK=24 K, γ of a few hundred mJ/molK2 and planar magnetic anisotropy χabc≈ 3 at low temperatures. Two magnetic transitions below 1 K can be fully suppressed with fields H<10 T. In going from low to higher H and T, the HT phase diagram down to 0.4 K shows a first-order transition from an antiferromagnetically ordered phase to a second magnetically ordered phase and then a second-order phase transition to a paramagnetic (field-polarised) phase. We have investigated YbAgGe for the first time down to 50 mK by measuring the resistivity ρ of single crystals in fields up to 14 T. Our results extend the HT phase diagram to the lowest temperatures for Hc and Hc. Whereas at low H, ρ(T) reveals a temperature exponent n≥ 2, close to and beyond the critical field of the second-order phase transition we find 1<n<1.5 and strong enhancement of the temperature dependence of ρ(T), before Fermi-liquid behaviour is recovered above 10 T. Particularities in the appearance of the unconventional form of ρ(T) will be discussed considering the HF nature and structural aspects of YbAgGe. YbAgGe appears to be one of few Yb-based stoichiometric systems, where quantum-critical behaviour may be induced by a magnetic field.

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