Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 18: Correlated Electrons: Spin Systems and Itinerant Magnets – Frustrated Magnets 2 (jointly with MA)
TT 18.9: Talk
Monday, March 16, 2015, 17:15–17:30, H 3005
Groundstate Entropy and Monopole Heat Transport in dilute Spin Ice — •S. Scharffe1, G. Kolland1, M. Valldor1,2, O. Breunig1, J. F. Welter1, P. Laschitzky1, and T. Lorenz1 — 1II. Physikalisches Institut, Universität zu Köln, Germany — 2Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany
The spin ice Dy2Ti2O7 is a geometrically frustrated spin system consisting of corner-sharing tetrahedra. An Ising anisotropy aligns the spins along their local easy axes in the 111 directions. Possible groundstates are given by the ”ice-rule”: two spins point into and two out of each tetrahedron. This behavior is analogous to the hydrogen displacement in water ice, revealing a residual entropy for T→ 0 K. Anomalous excitations are created by single spin flips and are discussed as magnetic monopoles which contribute to the magnetic heat transport in spin ice[1,2]. Here, specific heat and heat transport measurements of the pure spin ice and the diluted reference materials (Dy1−xYx)2Ti2O7 are presented. We extract cmag and demonstrate how the residual entropy of the pure spin ice varies with increasing non-magnetic Y-dilution. Additionally, we show that the monopole contribution κmag to the total heat transport also correlates with the degree of Y-dilution. The extraction of κmag and cmag enables us to calculate the magnetic diffusion coefficient Dmag of the spin-ice materials which is strongly suppressed in the diluted systems for T < 1 K.
This work was supported by the DFG via project LO 818/2-1.
[1] Kolland et. al., Phys. Rev. B, 86, 060402(R) (2012)
[2] Scharffe et. al., J. Magn. Magn. Mater. (in press, arXiv:1406.4037).