Tunable microwave properties of a skyrmion in an isolated nanodisk

Abstract

A magnetic skyrmion is a topological object having particle-spin like configuration, which can be stabilized in ferromagnetic systems with Dzyaloshinskii-Moriya interaction. In this report, we investigate tunable microwave properties of magnetic skyrmions in a circular nanodisk using micromagnetic simulations. An in-plane ac magnetic field excites gyrotropic dynamics with a clockwise and a counter-clockwise mode. We have shown the dependence of microwave responses on the size of the skyrmion by tuning the Dzyaloshinskii-Moriya interaction, magnetic anisotropy, and out-of-plane external bias magnetic field. A remarkably large frequency shift of 4.2 GHz has been observed for a change of 40 mT bias field. Furthermore, a broad microwave tunability of 10.8 GHz has been shown with a variation of magnetic anisotropy of 1 × 105 J/m3. The manifestation of inertial mass of the skyrmion, its dependence on the resonance responses and the sizes of the skyrmion are explained by using Thiele’s equation. The inertial mass of the skyrmion is estimated to be in the order of 10−23 kg. The results open up the potential use of the skyrmions in reconfigurable nano-magnonic devices with large tunability.