Connected-Skyrmions-Based Racetrack Memory

Magnetic skyrmions are used as binary digits of a domain motion-type magnetic memory such as racetrack memory. When two or more skyrmions are aligned on a track, a space must exist between each skyrmion. Eliminating this space would increase the storage density of racetrack memory. Thus, this study proposed the use of connected skyrmions as binary digits in racetrack memory and novel domain structures to remove this space. We proposed bi-skyrmion, i.e., two connected skyrmions, and tri-skyrmions, i.e., three connected skyrmions, having skyrmion numbers of 2 and 3, respectively. The connected skyrmions do not have a space between them. We investigate 2-, 3-, and 100-connected skyrmions produced in the nanowire, which is perpendicularly magnetized, using the micromagnetic simulation. The 2-, 3-, and 100-connected skyrmions can be stabilized in the wire. They were moved by the spin-polarized current in a manner similar to the skyrmion.