Twisted skyrmions at domain boundaries and the method of image skyrmions

摘要

We predict a twisted skyrmion structure at the boundary of two antiparallel magnetic domains stabilized by a (synthetic or crystal) antiferromagnetic coupling on the border. Through this novel state, skyrmions with opposite polarities can be freely switched between each other by spin-polarized electric currents. We therefore propose the concept of double-track skyrmion racetrack memories and logic gates where the binary data are represented by skyrmions with different polarities. The dynamics of the skyrmion polarity reversal is theoretically studied. Using the method of image, we derive the analytical formula of the repulsive potential when a normal skyrmion approaches the domain boundary. A harmonic attractive potential is obtained for the twisted skyrmion across the border. Micromagnetic simulations compare well with analytical results. The method of image skyrmion proposed in this work can be used to deal with a large class of skyrmion-boundary interaction problems.