Skyrmionium dynamics on a racetrack in the presence of a magnetic defect

Exotic topological textures known as skyrmioniums can stabilize in different types of ferromagnetic nanostructures. They possess a topological charge of Q = 0 and can move in straight lines unaffected by the skyrmion Hall effect. In this work, using micromagnetic simulations, we study the behavior of a skyrmionium when a polarized spin current transports it along a racetrack in the presence of a semicircular magnetic defect with different Dzyaloshinskii-Moriya interaction values. As a first step, we obtained the perpendicular uniaxial anisotropy (K z ) and the Dzyaloshinskii-Moriya constants (D int ) for which it is possible to form a skyrmionium in the racetrack. Our results show that the higher the K z value, the higher the D int values necessary to stabilize the skyrmionium. Furthermore, interaction energies between the skyrmionium and the semicircular defect are presented. The results show that the interaction energy can be attractive or repulsive, depending on the Dzyaloshinskii-Moriya defect interaction constant (D int def ). Finally, we conclude that using these types of defects and a spin-polarized current, the motion of the skyrmionium can be either modified in a specific way or even blocked.