# Field-tuned spin excitation spectrum of $k\pi$-skyrmion

## TL;DR

This study investigates the spin-wave excitation modes of $k extpi$ skyrmions in magnetic nanodots under external magnetic fields, revealing complex mode behaviors and transitions that could impact magnonics applications.

## Contribution

The paper provides the first detailed analysis of how $k extpi$ skyrmion spin-wave spectra evolve under external magnetic fields, highlighting new excitation modes and transition phenomena.

## Key findings

- Frequency of modes increases then decreases with magnetic field
- Higher $k$ skyrmions exhibit more excitation modes
- Mode frequencies vary significantly with magnetic field

## Abstract

We study spin-wave excitation modes of $k\pi$ skyrmion in a magnetic nanodot under an external magnetic field along $z$-direction using micromagnetic simulations based on Landau-Lifshitz-Gilbert equation. We find that a transition of $k\pi$ skyrmion to other skyrmion-like structures appears under some critical external field, the corresponding spin-wave spectra are simulated for each state in the process of applying magnetic field. For skyrmion, the frequencies of excitation modes increases and then decreases with the low frequency modes splitting at a critical magnetic field. In addition to the well known two in-plane rotational modes and a out-of-plane breathing mode of skyrmion, a higher number of excitation modes are found with increasing $k$ ($k=2, 3$). The excitation modes vary as a function of magnetic field, and the excitation frequencies for different modes exhibit a rapid or slight change depending on the field induced change of magnetization profile. Our study indicates the rich spin-wave excitations for $k\pi$ skyrmion and opens a possibility in theoretical or experimental investigation of magnonics application.