Hybrid finite-element/boundary-element method to calculate Oersted fields

The article presents a general-purpose hybrid finite-element/boundary-element method (FEM/BEM) to calculate magnetostatic fields generated by stationary electric currents. The efficiency of this code lies in its ability to simulate Oersted fields in complex geometries with non-uniform current density distributions. As a precursor to the calculation of the Oersted field, an FEM algorithm is employed to calculate the electric current density distribution. The accuracy of the code is confirmed by comparison with analytic results. Two examples show how this method provides important numerical data that can be directly plugged into micromagnetic simulations: The current density distribution in a thin magnetic strip with a notch, and the Oersted field in a three-dimensional contact geometry; similar to the type commonly used in spin-torque driven nano-oscillators. It is argued that a precise calculation of both, the Oersted field and the current density distribution, is essential for a reliable simulation of current-driven micromagnetic processes.