Optimization of electromagnet for high-field polar magneto-optical microscopy

Abstract

In this paper we propose a new method for simulation and optimization of the field of electromagnets. The method is applied to optimize the polar electromagnet with cylindrical symmetry for magnetooptic microscopy. The direct simulation is based on a discretization of Maxwell's equations by means of finite elements in the interior ferromagnetic parts that are coupled with boundary elements to model the exterior field. The ferromagnetic nonlinearity is treated by the Newton method. Further, we optimize shape of the ferromagnetics in order to achieve magnetic field above a pole head as high and as homogeneous as possible. The example of optimized electromagnet fits to a compact Zeiss polarization microscope adapted for polar magneto-optic domain visualization. Within the optimization we achieved the magnetic field of 0.23 T with inhomogeneity of 6% in a nonsaturated regime when applying a lower electric current, while in a saturated regime with a higher current applied the magnetic field was 0.47 T with inhomogeneity lower than 6%.