Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 8: Correlated Electrons: Spin Systems and Itinerant Magnets - Frustrated Magnets I
TT 8.3: Vortrag
Montag, 31. März 2014, 10:00–10:15, HSZ 304
Hysteresis and Relaxation Effects in the Spin-Ice Compound Dy2Ti2O7 studied by Heat Transport — •Simon Scharffe, Gerhard Kolland, Martin Hiertz, Martin Valldor, and Thomas Lorenz — II. Physikalisches Institut, Universität zu Köln, Germany
The magnetic Dy3+ ions in the spin ice Dy2Ti2O7 form a pyrochlore lattice consisting of corner-sharing tetrahedra. Due to strong crystal field effects an Ising anisotropy arises which aligns the spins along its local easy axis, pointing into or out of a tetrahedra. Possible ground-states at temperatures below 1 K are given by the ”ice rule”: two spins point into and two out of a tetrahedron. Excited states can be created by flipping one spin and are discussed as magnetic monopoles[1]. We measured the low-temperature thermal conductivity κ and found experimental evidence for heat transport by magnetic monopoles[2,3]. In addition we observe pronounced hysteresis effects which depend on temperature, the magnetic-field direction, the rate of magnetic-field change, and on the direction of the heat current. Moreover the time-dependent relaxation of the heat conductivity is investigated. These data yield information about possible equilibrium states and reveal that in the low-field and low-temperature region extremely slow relaxation processes occur[4].
This work was supported by DFG through SFB 608 and LO 818/2-1.
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