Acoustic–Electromagnetic Transformation in Magnetic Nanofuids

摘要

We examined the acoustic-electromagnetic transformation accompanying the propagation of sound wave through a magnetic nanofluid. Briefly the experimental procedure was as follows. The magnetic nanofluid was placed in the cylindrical resonator. An external magnetic field was applied along an axis of the cylindrical resonator. This field was obtained by means of a Helmholtz coil system. The induction coil was used to register local oscillations of the magnetic field. The signal was observed when the resonator was excited by the longitudinal sound wave with the frequency corresponding to one of the radial modes of the resonator. The parallel theoretical study supplies an interpretation of some of the experimental observations. An excitation of an electromagnetic field is shown to take place due to the perturbation in the magnetic permeability by a sound wave. It is shown that this effect can be used for the determination of ultrasound velocity and the average size of magnetic nanoparticles.