Finite-difference calculation of demagnetizing factors for shapes with cylindrical symmetry

The effect of the demagnetizing field plays an important part in determining the response to applied magnetic fields of samples which form incomplete magnetic circuits. The demagnetizing factor N is usually calculated using a surface magnetic charge model to deduce the demagnetizing held, In this work, a finite-difference method is used to calculate the flux density for a given applied field. The effective permeability mu(rod) is then deduced. N is calculated by comparing mu(rod) with mu(r), the intrinsic permeability of the material. Calculations for cylinders and ellipsoids give very good agreement with surface charge methods. Advantages of this approach include ease of application to more complex shapes and the potential for application to non-linear materials.