The Anisotropy of the Sound Attenuation in Magnetic Fluid under an External Magnetic Field

The sound attenuation coefficient of magnetic fluid under an external magnetic field varies with the angle φ between the field and the sound propagation. We attribute the cause of this anisotropy to the two motions of the clusters of the ferrous colloidal particles in the fluid. One is the rotational motion of them, which we analyze using liquid crystal theory, the other is the translational motion of them, which we analyze assuming the model of a vibrating sphere in viscous fluid. The theory interprets the two peaks of the attenuation coefficient curve ranging from φ=0 to φ=π/2.