Numerical Modeling of the Magnetoimpedance Effect from Micromagnetism

A new self-consistent (fully coupled) numerical method is proposed for modeling the magnetoimpedance effect directly from fundamental magnetic properties. It accounts for the dependence of the permeability on both the applied magnetic field and the amplitude of the alternating field produced by the current. This is particularly challenging because the local value of the ac field in the sample is, in turn, governed by the permeability due to the skin effect. First, using a micromagnetic code, the permeability is calculated for all combinations of the applied external field and amplitude of the ac field. The results are then transferred to a finite element program to solve the Maxwell equations, which self-consistently determines the appronriate permeability and the amplitude of the ac field in each point of the sample. Results are presented for a strip of Permalloy $500\ \mu\mathrm{m}$ long, 50 $\mu\mathrm{m}$ wide and 200 nm thick, confirming the effectiveness of the method to calculate the magnetoimpedance response from first principles.