A Methodology for Finite Element Modeling of Magnetic Inductive Devices With In-Plane Multidomain Pattern

We describe a method for using a commercially available three-dimensional electromagnetic finite-element program (Ansoft HFSS) for simulating the high-frequency (>100 MHz) magnetic response of multidomain inductive devices with in-plane easy-axis anisotropy. We calculate the impedance of a magnetic toroid with each of four multidomain patterns, and we compare the results obtained with HFSS to those using a standard micromagnetic package (NIST OOMMF) simulating a two-dimensional crosssection of the toroid. While there are differences between OOMMF and HFSS in the fine details of the impedance spectra, both predict a substantial inductance reduction above 200 MHz for the various multidomain toroids compared to a single-domain toroid. Based on an eigenmode calculation, this reduction of inductance is due to the presence of multiple magnetostatic modes that are strongest near the 180deg walls, with frequencies as low as 280 MHz for the material and geometry considered here