Mapping the magnonic landscape in patterned magnetic structures

TL;DR

This paper introduces a hybrid numerical and analytical model to map local ferromagnetic resonance frequencies and susceptibilities in patterned magnetic structures, aiding the design of magnonic devices.

Contribution

The paper presents a novel hybrid model combining micromagnetic simulations with analytical formalism to map spatially-varying magnetic properties in complex structures.

Findings

Successfully analyzed three non-uniform micromagnetic systems.

Explained spin-wave emission via the Schlömann excitation mechanism.

Demonstrated potential for guiding spin waves using magnetic non-uniformities.

Abstract

We report the development of a hybrid numerical / analytical model capable of mapping the spatially-varying distributions of the local ferromagnetic resonance (FMR) frequency and dynamic magnetic susceptibility in a wide class of patterned and compositionally modulated magnetic structures. Starting from the numerically simulated static micromagnetic state, the magnetization is deliberately deflected orthogonally to its equilibrium orientation, and the magnetic fields generated in response to this deflection are evaluated using micromagnetic software. This allows us to calculate the elements of the effective demagnetizing tensor, which are then used within a linear analytical formalism to map the local FMR frequency and dynamic magnetic susceptibility. To illustrate the typical results that one can obtain using this model, we analyze three micromagnetic systems boasting non-uniformity in either one or two dimensions, and successfully explain the spin-wave emission observed in each case, demonstrating the ubiquitous nature of the Schl\"omann excitation mechanism underpinning the observations. Finally, the developed model of local FMR frequency could be used to explain how spin waves could be confined and steered using magnetic non-uniformities of various origins, rendering it a powerful tool for the mapping of the graded magnonic index in magnonics.