Floating of solid non-magnetic bodies in magnetic fluids: Comprehensive analysis in the framework of inductive approach

This paper presents a study of the ponderomotive force acting on a solid non-magnetic sphere immersed in a magnetic fluid cylindrical container magnetized by an external homogeneous magnetic field. The problem has been studied experimentally, numerically, and analytically. The analytical study was carried out in the framework of the inductive approach, which made it possible to take into account the demagnetizing fields generated by both the magnetic fluid and the non-magnetic body. All methods of investigation used in this work showed the same non-standard force behavior with two extrema. The existence of the non-monotonous force is explained by the competition between two mechanisms: the inhomogeneous demagnetizing field inside the cylindrical container and the interaction of the solid body dipole with its own mirror image. The results of numerical simulations are in quantitative agreement with the experimental data, and the analytical results are in qualitative agreement with the experimental data.