EXPERIMENTAL INVESTIGATION OF THE DYNAMICS OF MICROSPHERES IN FERROFLUID

The motion of small nonmagnetic spheres confined in thin layers of ferrofluid subjected to a rotating magnetic field has been studied. No translational motion of the spheres was observed, but the rotating field induced a rotation of the spheres with direction opposite to that of the field rotation. The dependence of the sphere rotation on the frequency and strength of the field has been determined. The experiments showed that if a constant magnetic field was added normal to the rotating field, two adjacent microspheres stabilized at a fixed separation which was dependent upon the ratio between the constant and the rotating component of the field.