An irreversible magnetic-field dependence of low-temperature heat transport of spin-ice compound Dy_2Ti_2O_7 in a [111] field

TL;DR

This study investigates the low-temperature thermal conductivity of Dy_2Ti_2O_7 in a magnetic field, revealing irreversible behavior upon field cycling that suggests magnetic monopole pinning effects in spin ice.

Contribution

It reports the first observation of irreversible thermal conductivity behavior in Dy_2Ti_2O_7 related to magnetic field cycling, indicating monopole pinning effects.

Findings

Thermal conductivity shows step-like decreases at magnetic transitions.

Irreversible  H isotherms are observed at low temperatures.

Proposed magnetic monopole pinning as a possible cause.

Abstract

We study the low-temperature thermal conductivity (\kappa) of Dy_2Ti_2O_7 along and perpendicular to the (111) plane and under the magnetic field along the [111] direction. Besides the step-like decreases of \kappa at the field-induced transitions from the spin-ice state to the kagom\'e-ice state and then to the polarized state, an abnormal phenomenon is that the \kappa(H) isotherms show a clear irreversibility at very low temperatures upon sweeping magnetic field up and down. This phenomenon surprisingly has no correspondence with the well-known magnetization hysteresis. Possible origins for this irreversibility are discussed; in particular, a pinning effect of magnetic monopoles in spin ice compound by the weak disorders is proposed.