Regensburg 2016 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 3: Correlated Electrons: Frustrated Magnets - Pyrochlore Systems and Iridates
TT 3.4: Vortrag
Montag, 7. März 2016, 10:15–10:30, H20
Suppression of Pauling’s residual entropy in dilute spin ice (Dy1-xYx)2Ti2O7 — •S. Scharffe1, O. Breunig1, V. Cho1, P. Laschitzky1, M. Valldor1,2, J. F. Welter1, 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 with an Ising anisotropy that aligns the spins along their local easy axes in the 111 direction. In the ground state configuration two spins point into and two out of each tetrahedron. The entropy of Dy2Ti2O7 reveals a plateaulike feature close to Pauling’s residual entropy around 0.5 K derived originally for water ice, but a distinct expansion towards lower temperature is prevented by ultraslow thermal equilibration. We present specific-heat data of (Dy1-xYx)2Ti2O7 and analyze the influence
of nonmagnetic yttrium dilution on the low-temperature entropy. We find that these ultraslow thermal equilibration
rapidly vanishes with increasing x, the low-temperature entropy systematically decreases, and its temperature dependence strongly increases[1]. From our data, a nondegenerate ground state can be derived for (Dy1-xYx)2Ti2O7 with intermediate dilution. This is in contrast to an expected zero-temperature residual entropy obtained from a generalization of Pauling’s theory for dilute spin ice, but is supported by Monte Carlo simulations which are also compared to our results.
This work was supported by the DFG via project LO 818/2-1.
[1] Scharffe et al., PRB, 92, 180405(R) (2015)