Critical behavior of sound attenuation in a metamagnetic Ising system

In this study, the sound attenuation coefficient of a spin- metamagnetic Ising system is calculated by the method of thermodynamics of irreversible processes. The behavior of sound attenuation near the phase transition temperatures is analyzed according to various values of phenomenological rate coefficients (γij). For all γm and γs values it is found that sound attenuation peaks occur below TN(H) and depend on frequency ω and the value of the off-diagonal rate coefficient γ. On the other hand, the critical behavior of the sound attenuation in the hydrodynamic regime is obtained analytically via the critical exponents. Moreover, the behavior of the sound attenuation as a function of frequency is also investigated and ω² dependence is observed for the attenuation coefficient. These results are in a good agreement with ultrasonic investigations of magnetic systems.