Frequency dependences of the velocity and absorption coefficient of sound waves in a magnetic fluid

On the basis of molecular-kinetic theory, frequency-dependent expressions are derived for the velocity and absorption coefficient of sound in a magnetic fluid with allowance for the contribution of structural relaxation in the presence of an external inhomogeneous magnetic field. The asymptotic behavior of the expressions is investigated for both low-and high-frequency limits. A numerical study is carried out by taking as an example a magnetic fluid consisting of kerosene with magnetic particles of Fe₃O₄ suspended in it. The results of the numerical study show that the calculated frequency dependences of the velocity and absorption coefficient of sound in a magnetic fluid are in good agreement with the static experimental data.