Temperature Dependence of Acoustic Attenuation in Ferrous Oxide (FeO)

The present article deals with the attenuation of acoustic waves propagating through Ferrous Oxide (FeO) based on a theory developed by W.P. Mason. The Second Order Elastic Constants (SOEC) of the material have been used to find the Gruneisen constants <Upsilon(j)(i)> and its square average, using which the non-linearity parameter D has been evaluated at different temperatures. The acoustic attenuation coefficient per unit frequency square due to phonon-phonon interaction for longitudinal waves [proportional to / f(2)](S) and shear waves [proportional to / f(2)](L), and that due to thermoelastic losses [proportional to / f(2)](th) are calculated along the <100 > crystallographic axis, within the temperature range 373-673 K. The non-linearity parameters D-L and D-S which account for the anharmonicity of the material are found to be dependent on the temperature and increase with it. The study shows that the magnitude of [proportional to / f(2)] due to phonon-phonon interaction, for both longitudinal and shear waves is of the order 10(-16) dbs(2)m(-1), while, for thermoelastic losses, it is of the order 10(-18) dbs(2)m(-1). Thus, it can be observed that phonon-phonon interaction is the prominent cause of acoustic attenuation of the propagating waves and the contribution due to thermoelastic losses is very small. The study also shows that the longitudinal waves are more attenuated as compared to shear waves, as they propagate through the solid medium and suffer more amplitude losses. This work can be useful for the characterization and study of the anharmonic behavior of crystals as well as attenuation studies in other similar oxide crystals.