Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 78: Correlated Electrons: Poster Session

TT 78.11: Poster

Donnerstag, 10. März 2016, 15:00–18:30, Poster D

Fluctuation dynamics near the quantum critical point in the S=1/2 Ising chain CoNb₂O₆ — •Steffen Harms, Johannes Engelmayer, Thomas Lorenz, and Joachim Hemberger — II. Physikalisches Institut, University of Cologne, Germany

CoNb₂O₆ is a model system for quantum phase transitions in magnetic field. Its structure consists of layers of CoO₆ octhahedrons separated by non-magnetic NbO₆ layers. The edge-sharing oxygen octahedrons link the Co²⁺spins via Co-O-Co superexchange and form 1D ferromagnetic zigzag chains along the orthorhombic c axis. Crystal field effects lead to an easy-axis anisotropy of the Co²⁺ moments in the ac plane and to an effective spin-1/2 chain system. The 1D spin system can be described by the Ising model. At T=0K a transverse magnetic field can induce a quantum phase transition from a long range ferromagnetic state into a quantum paramagnetic state. Employing measurements of the complex AC-susceptibility in the frequency range 10MHz < ν < 5GHz for temperatures down to 50mK we investigate the slowing down of the magnetic fluctuation dynamics in the vicinity of the critical field at µ₀H=5.25T [1].

Funded through the Institutional Strategy of the University of Cologne within the German Excellence Initiative.
: A.W. Kinross et al. PRX 4, 031008 (2014)