The influence of curved surfaces on the propagation of skyrmions in a magnetic racetrack

Abstract

The purpose of the current study is to analyze the effect of curvature on magnetic skyrmions by micromagnetic simulations. It is divided into two parts: First, we studied the stability of skyrmions on CoPt cylindrical surfaces, analyzing the static conditions for the annihilation of skyrmions as a function of the radius and curvature (positive or negative) of the surface. Unlike planar geometry, the skyrmion can be deformed into an elliptical shape when the surface is curved. In the second part, we analyzed the skyrmion dynamics when a spin-polarized current density is applied to a CoPt racetrack with a geometric defect in the form of a cylindrical surface, intercalated in the racetrack. We studied the conditions for skyrmion annihilation and compared it with the static case on cylindrical surfaces for various values of the radius and width of the geometric defect and also for various intensities of spin-polarized current density. We analyzed the shape of the skyrmion by measuring its radius in two perpendicular directions and its dynamic behavior when going through of the geometric defect, measuring the position and velocities of the skyrmion’s center. Furthermore, we compared the velocity profile obtained in the simulation with the theoretical results obtained by the Thiele’s equation as a function of the radius and width of the geometrical defect, and we showed that skyrmion can be accelerated and its speed can be increased up to 14 times due to an induced force (repulsive and attractive) that arises in the geometric defect region. Our results are in agreement with the results using the Thiele’s equation.