Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 13: Magnetic Materials
MA 13.6: Vortrag
Montag, 26. März 2012, 16:15–16:30, H 0112
Magnetic order and quantum criticality in single-crystalline NbFe2 — •Sven Friedemann1, Max Hirschberger1,2, Megan Stanley1, William J Duncan1, Andreas Neubauer2, Thomas Bauer3, Robert Küchler3, Alexander Steppke3, Luis Pedrero3, Manuel Brando3, Christian Pfleiderer2, and F Malte Grosche1 — 1Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK — 2Physik Department E21, TU München, 85748 Garching, Germany — 3Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
The low-temperature band magnet NbFe2 can be tuned by varying pressure, magnetic field or composition, providing an attractive candidate system for investigating quantum criticality in a transition metal compound. Near the composition-tuned quantum critical point, NbFe2 displays signatures of Fermi liquid breakdown in the electronic heat capacity Δ C ∼ −T lnT and in the resistivity Δρ ∼ T3/2 at low temperature T. Our data on high-quality single crystals confirm the existence of a non-ferromagnetic phase via distinct transition anomalies in the field dependence of the entropy. This presumed spin-density-wave phase envelops the lower-lying ferromagnetic phase in most parts of the composition–field–temperature phase diagram. The associated transition temperature can be suppressed with a transverse magnetic field ( ⊥ c). Consequently, transverse field is identified as a further tuning parameter, which leads to a direct transition from the ferromagnetic to a field-induced paramagnetic state. In the vicinity of this quantum phase transition, we observe a suppression of Fermi liquid behaviour.