Dynamical susceptibility of Skyrmion crystal

TL;DR

This paper develops an analytical theory to calculate the dynamical susceptibility tensor of Skyrmion crystals in thin ferromagnetic films, predicting multiple resonance frequencies observable in magnetic resonance experiments.

Contribution

It introduces a new analytical framework for the dynamical susceptibility of Skyrmion crystals, including small fluctuations and additional resonance predictions.

Findings

Identification of multiple resonance frequencies in SkX susceptibility

Prediction of smaller amplitude resonances at higher frequencies

Analytical formulas applicable to magnetic resonance experiments

Abstract

Using stereographic projection approach we develop a theory for calculation of dynamical susceptibility tensor of Skyrmion crystals (SkX), formed in thin ferromagnetic films with Dzyaloshinskii-Moriya interaction and in the external magnetic field. Staying whenever possible within analytical framework, we employ the model anzats for static SkX configuration and discuss small fluctuations around it. The obtained formulas are numerically analyzed in the important case of uniform susceptibility, accessible in magnetic resonance (MR) experiments. We show that, in addition to three characteristic MR frequencies discussed earlier both theoretically and experimentally, one should also expect several resonances of smaller amplitude at somewhat higher frequencies.