Thermal Relaxation and Heat Transport in the Spin Ice Material Dy2Ti2O7

Abstract

The thermal properties of single crystalline Dy2Ti2O7 have been studied in a temperature range from 0.3 K to 30 K and magnetic fields applied along [110] direction up to 1.5 T. Based on a thermodynamic field theory various heat relaxation and thermal transport measurements were analysed. So we were able to present not only the heat capacity of Dy2Ti2O7 in the whole temperature and magnetic field range, but also the different contributions of the magnetic excitations and their corresponding relaxation times in the spin ice phase. In addition, the thermal conductivity and the shortest relaxation time were determined by thermodynamic analysis of steady state heat transport measurements. Finally, we were able to reproduce the temperature profiles recorded in heat pulse experiments on the basis of the thermodynamic field theory using the previously determined heat capacity and thermal conductivity data without additional parameters. Thus, the thermodynamic field theory has been proved to be thermodynamically consistent in describing three thermal transport experiments on different time scales. The observed temperature and field dependencies of heat capacity contributions and relaxation times indicate the magnetic excitations in the spin ice material Dy2Ti2O7 as thermally activated monopole-antimonopole defects.