Ferromagnetic resonance in systems with competing uniaxial and cubic anisotropies

TL;DR

This paper presents a comprehensive model for ferromagnetic resonance in systems with both uniaxial and cubic anisotropies, including numerical and analytical methods to analyze resonance behavior and estimate anisotropy constants.

Contribution

It introduces a new model and analytical expressions for ferromagnetic resonance in systems with competing anisotropies, aiding experimental data analysis.

Findings

Numerical computation of resonance frequency and field as functions of anisotropy ratio.

Analytical expressions for weak cubic anisotropy cases.

Method for estimating anisotropy constants from resonance data.

Abstract

We develop a model for ferromagnetic resonance in systems with competing uniaxial and cubic anisotropies. This model applies to (i) magnetic materials with both uniaxial and cubic anisotropies, and (ii) magnetic nanoparticles with effective core and surface anisotropies; We numerically compute the resonance frequency as a function of the field and the resonance field as a function of the direction of the applied field for an arbitrary ratio of cubic-to-uniaxial anisotropy. We also provide some approximate analytical expressions in the case of weak cubic anisotropy. We propose a method that uses these expressions for estimating the uniaxial and cubic anisotropy constants, and for determining the relative orientation of the cubic anisotropy axes with respect to the crystal principle axes. This method is applicable to the analysis of experimental data of resonance type measurements for which we give a worked example of an iron thin film with mixed anisotropy.