Dynamical switching of confined magnetic skyrmions under circular magnetic fields

Understanding the dynamical properties of magnetic skyrmions is of prime importance for realization of skyrmion based devices. Here we report on the dynamics of a confined magnetic skyrmion under application of circular magnetic fields (CMFs). We provide the complex map of the dynamical states and demonstrate that under some conditions CMFs can change the skyrmion number and lead to the switching of the core polarity. Combing the results of micromagnetic simulations with those of analytical calculations, based on the extended Thiele equation, we unravel the physical mechanism behind this dynamical switching. The core switching is associated with the dynamical motions of the skyrmion driven by a CMF. The formation of domain walls and their movement from the border towards the center leads to shrinking of the skyrmion and the creation of a skyrmion with opposite core polarity. The results provide a guideline for checking the skyrmion's stability as well as an efficient way for switching the core polarity using CMFs.