Spin pinning and spin-wave dispersion in nanoscopic ferromagnetic waveguides

TL;DR

This paper investigates spin waves in ultra-thin YIG waveguides with varying widths, revealing a critical width where exchange interactions alter spin-wave mode quantization, supported by experiments, theory, and simulations.

Contribution

It introduces a semi-analytical theory to calculate spin-wave modes and dispersion in nanostructures, highlighting the impact of exchange interactions on pinning phenomena.

Findings

Identification of a critical width where dipolar pinning is suppressed

Modification of spin-wave eigenmode quantization criteria

Agreement between experimental results, theory, and simulations

Abstract

Spin waves are investigated in Yttrium Iron Garnet (YIG) waveguides with a thickness of 39 nm and widths ranging down to 50 nm, i.e., with aspect ratios thickness over width approaching unity, using Brillouin Light Scattering spectroscopy. The experimental results are verified by a semi-analytical theory and micromagnetic simulations. A critical width is found, below which the exchange interaction suppresses the dipolar pinning phenomenon. This changes the quantization criterion for the spin-wave eigenmodes and results in a pronounced modification of the spin-wave characteristics. The presented semi-analytical theory allows for the calculation of spin-wave mode profiles and dispersion relations in nano-structures.