Localized Spin-Wave Modes and Microwave Absorption in Random-Anisotropy Ferromagnets

TL;DR

This paper develops a theoretical framework for understanding localized spin-wave modes in random-anisotropy ferromagnets, linking localization phenomena to microwave absorption properties.

Contribution

It introduces a comprehensive theory describing how increasing random anisotropy leads to localized spin-wave modes and their impact on microwave absorption in finite-size ferromagnetic samples.

Findings

Localization length increases with random anisotropy strength

Localized modes exhibit distinct phase profiles

Microwave absorption broadens due to localized spin excitations

Abstract

The theory of localized spin-wave excitations in random-anisotropy magnets has been developed. Starting with a pure Heisenberg ferromagnet, we study the evolution of standing spin waves in a finite-size sample towards localized modes on increasing the strength of random anisotropy. Profiles of the localized modes and their phases are analyzed and visualized in a 2D sample. Localization length is obtained by several methods and its dependence on random anisotropy is computed. The connection between the localization of spin excitations and the broadband nature of the absorption of microwave power by random-anisotropy magnets is elucidated.