Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 2: Quantum-Critical Phenomena

TT 2.9: Vortrag

Montag, 26. März 2007, 11:45–12:00, H19

Logarithmic Fermi-liquid breakdown in Nb_1.02Fe_1.98 — •Manuel Brando¹, Dennis Moroni-Klementowicz², Carsten Albrecht², William Duncan², Daniel Gruener¹, Guido Kreiner¹, Rafik Ballou³, Bjorn Fak⁴, and Malte Grosche² — ¹Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Strasse 40, D-01187 Dresden, Germany — ²Dept. of Physics, Royal Holloway, University of London, Egham TW20 0EX, UK — ³Laboratoire Louis Néel, CNRS, B.P. 166, 38042 Grenoble Cedex 9, France — ⁴Commissariat à l’Energie Atomique, Département de Recherche Fondamentale sur la Matière Condensée, SPSMS, 38054 Grenoble, France

We report measurements of the heat capacity C and of the resistivity ρ in stoichiometric and slightly Nb-rich NbFe₂ samples, including a single crystal with the composition Nb_1.02Fe_1.98, which on the phase diagram is located very close to the quantum critical point (T_N≃ 2.8K). Both the resistivity and the heat capacity of the nearly quantum-critical single crystal display striking, robust non-Fermi liquid temperature dependences: while the heat capacity coefficient γ=C/T diverges weakly as C/T ∼ logT from 4K down to 0.1K, in line with theoretical predictions for 3-D ferromagnetic quantum criticality, the resistivity follows a T^3/2 power-law, familiar from the case of MnSi and naively predicted for the proximity of an antiferromagnetic quantum critical point.