Thermoelastic relaxation near the Curie point of EuO

Abstract

An extensive investigation of the acoustic properties of thin EuO reeds has been carried out near the magnetic critical temperature $T_C=69.3\mathrm{}$ K. The main results are the observation of an enhanced damping and velocity dispersion of flexural modes in the frequency range 0.4-3 kHz as $T\to T_C$. These experimental findings are quantitatively described by Zener's theory of thermoelastic relaxation, taking into account the strong temperature dependences of thermodynamic and transport properties near $T_C$. The temperature dependences of the adiabatic and isothermal Young's-modulus sound velocities are also obtained. Pippard relations are used to determine the thermodynamic quantities ($\frac{dP}{dT}$), ($\frac{dS}{dT}$), and ($\frac{dS}{dP}$) along the transition line.