Spin Diffusion in 2D XY Ferromagnet with Dipolar Interaction

TL;DR

This paper investigates how dipolar interactions affect spin-wave excitations in a 2D XY ferromagnet, revealing a transition from soft modes to anisotropic diffusion at different wavelengths.

Contribution

It introduces a novel analysis of dipolar-induced interactions on spin-wave excitations using the Janssen-De-Dominicis method in a 2D XY ferromagnet.

Findings

Identification of a transformation into a soft-mode excitation at intermediate wavelengths.

Discovery of an anisotropic diffusion mode at long wavelengths.

Observation of highly anisotropic dissipation at short wavelengths.

Abstract

In the ordered phase of 2D XY ferromagnet the dipolar interaction between spins induces a strong, relevant interaction between spin-waves. We study quasi-excitations of the interacting spin-wave 'liquid' in the long wavelength limit. We employ the Janssen-De-Dominicis method for classical Langevin equation to find the transformation of the spin-wave excitation into a new soft-mode excitation in the intermediate range of wavelengths; and into an anomalous anisotropic diffusion mode excitation at long wavelengths. The dissipation of a spin-wave at short wavelengths is found to be highly anisotropic.