Thermal Expansion in Dysprosium Aluminum Garnet

Abstract

We have observed the Néel‐point anomaly in the linear thermal expansion coefficient α of dysprosium aluminum garnet using the three‐terminal capacitance technique. The shape of the λ peak at 2.53°K is similar to the specific‐heat peak reported by Keen, Landau, and Wolf, although our measurements have less resolution since the relative length change from 1°–4°K is only approximately 2×10⁻⁷. For |1‐T/T_N|TN and with a power law behavior for T>T_N. The predominant magnetic interaction is the dipolar coupling of the Dy³⁺ ions. We use a thermodynamic relation between the expansion coefficient and the specific heat at the λ transition to estimate ‐ ∂ logT_N/∂logV=1.0±0.5 in agreement with theoretical expectations for dipolar coupling.