The role of the internal demagnetizing field in a surface-modulated magnonic crystal

TL;DR

This paper investigates how local demagnetizing fields influence spin-wave behavior in surface-modulated magnonic crystals, combining experimental electron holography with dynamic simulations to reveal their key role in spin dynamics.

Contribution

It demonstrates the significant impact of internal demagnetizing fields on spin-wave properties in surface-modulated magnonic crystals through combined experimental and simulation approaches.

Findings

Internal field landscape governs spin-wave localization.

Angular dependence of spin waves explained by internal fields.

Simulations match experimental frequency-field behavior.

Abstract

Magnonic crystals with locally alternating properties and specific periodicities exhibit interesting effects, such as a multitude of different spin-wave states and large band gaps. This work aims for demonstrating and understanding the key role of local demagnetizing fields in such systems. To achieve this, hybrid structures are investigated consisting of a continuous thin film with a stripe modulation on top favorable due to the adjustability of the magnonic effects with the modulation size. For a direct access to the spin dynamics, a magnonic crystal was reconstructed from `bottom-up', i.e., the structural shape as well as the internal field landscape of the structure were experimentally obtained on the nanoscale using electron holography. Subsequently, both properties were utilized to perform dynamic response calculations. The simulations yield the frequency-field dependence as well as the angular dependence of spin waves in a magnonic crystal and reveal the governing role of the internal field landscape around the backward-volume geometry. The complex angle-dependent spin-wave behavior is described for a 360 degree in-plane rotation of an external field by connecting the internal field landscape with the individual spin-wave localization.