Dresden 2014 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 8: Correlated Electrons: Spin Systems and Itinerant Magnets - Frustrated Magnets I
TT 8.3: Talk
Monday, March 31, 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.
Castelnovo et al., Nature 451 (2008) 42
Kolland et al., Phys. Rev. B, 86 (2012) 060402(R)
Kolland et al., Phys. Rev. B, 88 (2013) 054406
Scharffe et al., J. Phys. Soc. Jpn. Suppl. (in press), arXiv:1311.1139