Session P31: Focus Session: Spin Ice

8:00 AM–11:00 AM, Wednesday, March 18, 2009
Room: 335

Sponsoring Unit: GMAG
Chair: Oleg Tchernyshyov, Johns Hopkins University

Abstract ID: BAPS.2009.MAR.P31.1

Abstract: P31.00001 : Magnetothermodynamics of spin ice and related compounds

8:00 AM–8:36 AM

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Author:

  Xianglin Ke
    (The Pennsylvania State University)

Geometrically magnetic frustration, which results from the competition of spin-spin interactions of magnetic ions on a regular magnetic lattice, leads to a variety of exotic low temperature states including ``spin ice.'' ``Spin ice'' refers to a magnetic state wherein the two-in/two-out spin configurations of rare earth pyrochlore compounds mimic the proton positions in the water ice, characterized by the ``zero point entropy'' of (R/2) ln(3/2). In this study, we examine how structural disorder affects spin dynamics and the magnetic ``zero point entropy.'' By diluting the ``spin ice'' materials with nonmagnetic ions on the rare earth sites, we have found that the entropy of the diluted species depends non-monotonically on the dilution concentration, and we explain this behavior using a generalized Pauling approximation. Nonmagnetic doping on B sites leads to only a small decrease of the ``zero point entropy,'' indicating the robust nature of ``spin-ice.'' We have also studied Dy2Ge2O7, which has the same chemical formula as ``spin ice'' materials and Ising-like spins but a tetragonal structure. Dy2Ge2O7 undergoes a long range antiferromagnetic ordering transition, but the spin dynamics at temperatures above the order transition is similar to that observed in the canonical ``spin ice'' systems, suggesting that such dynamics are generic to a broader class of Ising-like rare earth systems. \\[4pt] References: \\[0pt] [1] X. Ke \textit{et al}., Phys. Rev. Lett. \textbf{99}, 137203 (2007).\\[0pt] [2] X. Ke \textit{et al}., Phys. Rev. B. \textbf{76}, 214413 (2007).\\[0pt] [3] X. Ke \textit{et al}., Phys. Rev. B. 7\textbf{8}, 104411 (2008).

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.P31.1