The Vortex Core Switching by Bloch Point Pair

In a confined ferromagnetic disk, the magnetic vortex structure, one of magnetic topological texture, has been considered as a good candidate for developing information storage and processing device due to its tiny size and high thermal stability. In addition, its rich dynamic properties, such as gyrotropic mode, azimuthal and radial spin wave modes, shows the potential to develop nano-oscillator. The magnetic vortex is composed of the vortex core at the center and in-plane curling magnetization. There are energetically fourfold states of magnetic vortex with the combination of the vortex core polarization and in-plane curling magnetization. It is well known that the magnetic vortex core can be switched through the injection of the Bloch point on the surface of the disk. In this work, we will report that the vortex core switching by Bloch point pair in the circular shaped permalloy (Ni80Fe20, Py) disk through the resonant excitation of a three-dimensional (3D) dynamic mode, a size oscillation of the vortex core. We found that the Bloch point pair is nucleated in the internal region, not surface. Our work provides understanding 3D dynamic nature of magnetic vortex with a method to achieve ultrafast vortex core reversals