Skyrmion dynamics and the Skyrmion-Excited Spin Wave Fractal Network

Magnetic skyrmions are topologically protected spin textures which have been of interest for both their fundamental qualities as well as applications in data storage and logic technologies. Recently, there has been an emphasis on dynamic modes in the skyrmions. These investigations have revealed a rich collection of fundamental physics, including a variety of discrete excitation modes far beyond simple gyration and breathing mechanisms. In this work, we perform small angle neutron scattering (SANS) while performing in-situ ferromagnetic resonance (FMR), using the reciprocal space diffraction pattern as a direct probe of the skyrmion dynamic modes. The observations revealed the fairly benign conclusion that the skyrmion lattice remained largely unchanged during its dynamic modes, however, additional scattering was observed at ultra-small angles. This scattering was well fit by a mass-fractal model, which is generally representative of a network constructed from monodisperse elements, such as a polymer matrix. Using micromagnetic modeling to support our investigation, this network was revealed to be the consequence of spin waves and spin wave interference, forming a spin wave fractal network.