How to write, delete, and drive skyrmions

Skyrmions were originally proposed by British physicist Tony Skyrme in the 1960s as topological solitons to account for the stability of baryons in particle physics. Realization of skyrmions as vortex-like swirling spin textures was discovered in ferromagnets with chiral crystal symmetry, in which ferromagnetic-exchange interactions favoring parallel spin alignment and Dzyaloshinskii-Moriya interactions favoring rotational spin alignment strongly compete. Subsequent studies have revealed that skyrmions possess numerous advantageous properties for application to information carriers in high-density and low-energy-consuming magnetic memories and logic devices. These properties are: (1) topologically protected stability, (2) small nanometric size, (3) rather high transition temperatures, and (4) ultralow fields or electric currents to drive their motion. This article first introduces fundamental properties of skyrmions and skyrmionic materials and then presents recent attempts and ideas on writing, deleting, and driving skyrmions towards establishing their functions in memory devices. (author)