Glass-Forming Spin-Liquid States in the Frustrated Magnets Dy2Ti2O7 and Ho2Ti2O7

Dr. Anna Eyal (hosted by Zohar Nussinov), Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, N.Y.
November 6, 2017 at 4:00 pm
241 Compton
Event Description 

The ground states and low temperature characteristics of frustrated magnetic systems offer a variety of novel magnetic states. Among these are the pyrochlore magnetic insulators Dy2Ti2O7 and Ho2Ti2O7, for which despite a well-ordered crystal structure and strong magnetic interactions between the Dy3+ or Ho3+ ions, no long-range magnetic order has been detected. The low-temperature magnetic state in these materials is governed by spin-ice rules, in analogy to water ice. These constrain the Ising-like spins in the materials, yet does not result in a global broken symmetry state.

To explore the actual magnetic phase formed by cooling these materials, we measured their magnetization dynamics using toroidal, boundary-free magnetization transport techniques. We find that the dynamical magnetic susceptibility of both Dy2Ti2O7 and Ho2Ti2O7 has the same distinctive phenomenology, that is indistinguishable in form from that of the dielectric permittivity of dipolar glass-forming liquids. Moreover, Dy2Ti2O7 and Ho2Ti2O7 both exhibit microscopic magnetic relaxation times that increase along the super-Arrhenius trajectories analogous to those observed in glass-forming dipolar liquids.

Thus, upon cooling below about 2K, Dy2Ti2O7 and Ho2Ti2O7 both appear to enter the same magnetic state exhibiting the characteristics of a glass-forming spin-liquid. I will discuss how this striking phenomenology can be consistent with magnetization dynamics based on magnetic-monopole transport in these canonical pyrochlore titanates, and how differences in the spin dynamics between the two materials investigated, specifically in their measured time scales, can be consistent with the dynamics of such magnetic monopole excitations.

 

Coffee:  3:45 pm, 241 Compton