Magnetic skyrmions generation and control in FePt nanoparticles through shape and magnetocrystalline anisotropy variation: a finite elements method micromagnetic simulation study

Abstract Magnetic skyrmions created during magnetization reversal in cylindrical, reuleaux and polygon-based magnetic nanoparticles with perpendicular magnetocrystalline anisotropy (MCA) similar to that of partially chemically ordered FePt were studied using finite elements method micromagnetic simulations. Néel chiral stripes, horseshoe, labyrinth skyrmionic textures along with multiple skyrmions were unveiled in different systems generated by the variation of the MCA magnitude and the nanoparticles geometrical shape. These skyrmionic textures under certain conditions can be stable in a range of external magnetic fields and for different MCA values. Simulations revealed the inherent relation of skyrmionic states with nanoparticle geometry and the energy differences between successive external field values observed during the magnetization reversal process. Energetical transitions from non-skyrmionic to skyrmionic and from skyrmionic to different skyrmionic states were quantified and associated with the individual anisotropy, exchange and demagnetization energy contributions for the nanoparticles studied. Finally, the diameters of Néel type skyrmions created through the nanoparticle shape variation were reported for different MCA and external magnetic field values.