Shaping magnetic fields with soft ferromagnets: Application to levitation of superconductors

Soft ferromagnetic materials have an important role in technology, for increasing magnetic field in specific regions, as in the core of transformers, and for properly modifying the magnetic field in particular shapes. Here we develop a numerical model that allows study of the response of a soft ferromagnet bar with arbitrary cross section and infinite susceptibility when a magnetic field with translational symmetry is applied. This theoretical tool will enable us to analyze the shape and position of the soft ferromagnet to properly modify the magnetic field in the areas of interest. The model can also simulate hybrid systems that contain a superconducting bar as well, considering the mutual interaction between the soft ferromagnetic and the superconducting materials. In particular, we analyze the levitation force of a superconducting bar immersed in the magnetic field created by a guideway of two permanent magnet bars with uniform horizontal magnetization and a soft ferromagnet bar in between. The results show that by placing the soft ferromagnet with an optimized height the levitation force is enhanced. (C) 2012 American Institute of Physics. [doi:10.1063/1.3676578]