Magnetic textures in topological magnetic nanoparticles*

Magnetic materials with the requisite inversion-breaking needed for nonzero Dzyaloshinskii-Moriya interaction (DMI) can host a variety of exotic noncollinear spin textures, including skyrmions. Investigating topological materials in a nanoparticle system holds promise to demonstrate novel spin textures due to the increased number of possible symmetries and length scales compared to bulk and thin-film systems. We use spin dynamics simulations to characterize the magnetic textures of cubic nanoparticles as they undergo a field-cooling, producing phase diagrams of the topological charge with variation of the DMI and external field. These simulations are motivated by ab initio calculations of DMI in nanoparticles that demonstrate strong chiral interaction resulting from structural inversion asymmetry at the nanoparticle surface. Therefore, a symmetry analysis is used to determine DMI direction. Our results show the penetration of the surface texture into the bulk-like interior even for a simple model, and serve as guidance for future inquiries into topological nanoparticles.