Dresden 2017 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 68: Poster 5

MA 68.15: Poster

Freitag, 24. März 2017, 09:30–13:00, P2-OG4

Monopole heat transport and residual entropy in dilute spin ice (Dy1−xYx)2Ti2O7 — •Daniel Brüning, Simon Scharffe, Jean-Francois Welter, Gerhard Kolland, and Thomas Lorenz — II. Physikalisches Institut, Universität zu Köln, Deutschland

The spin ice Dy2Ti2O7 is a geometrically frustrated spin system of corner-sharing tetrahedra with an Ising anisotropy. In the ground state configuration two spins point into and two out of each tetrahedron. The lowest excitation in spin ice systems is a single spin flip which creates a pair of 1in-3out and 3in-1out configurations on neighboring tetrahedra. Such a pair can fractionalize into two individual excitations, namely magnetic monopoles, that can propagate almost independently within the pyrochlore lattice. The entropy of Dy2Ti2O7 reveals a plateau-like feature close to Pauling’s residual entropy around 0.5 K derived originally for water ice. Ultraslow thermal equilibration prevents a distinct expansion towards lower temperature. We analyze the influence of non-magnetic yttrium dilution on the low-temperature entropy of (Dy1−xYx)2Ti2O7. The ultraslow thermal equilibration rapidly vanishes with increasing x, the low-temperature entropy systematically decreases, and its temperature dependence strongly increases. From our data, a non-degenerate ground state can be derived that is compared to different theoretical approaches. Additionally, we present the heat transport data of the dilution series, which give insight in the monopole transport contribution.

Supported by the DFG via CRC 1238 and project LO 818/2-1.

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