Berlin 2005 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
TT: Tiefe Temperaturen
TT 3: Correlated Electrons - Heavy Fermions
TT 3.7: Vortrag
Freitag, 4. März 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 Flouquet1 — 1SPSMS/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 χab/χc≈ 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 H−T 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 H−T phase diagram to the lowest temperatures for H⊥ c and H∥ c. 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.