Cylindrical magnetization model for glass-coated microwires with circumferential anisotropy: Dynamics

The high frequency magnetic susceptibility of glass-coated microwires with effective circumferential anisotropy has been modeled by micromagnetics. In their amorphous and magnetically soft metallic nucleus, the negative magnetostriction induces a continuous and non-uniform vortex-like structure, with an axially magnetized core coupled to a circumferentially magnetized outer shell. The model is a one-dimensional radial micromagnetic model where exchange, magnetoelastic and magnetostatic energies are considered. The microwave permeability under AC (axial and circumferential) fields is found to be expressed as a sum over a set of eigenmodes, each with a characteristic resonance frequency. In the framework of this model, a sum rule on the frequency-dependent permeability is shown to hold. It provides a figure of merit and guidelines for the design of high permeability materials for applications in the microwave range.

► We model the magnetization dynamics for microwires with non-uniform structure. ► The microwave response depends on radius, exchange, anisotropy and external fields. ► The permeability spectra are computed as the sum of radial spin waves. ► Both axial and circumferential AC field orientations are considered. ► The permeability level and resonance peak are different from macrospin predictions.