Principle of magneto-optic memories. Up and down domains correspond to logical 0 and 1. The formation of a domain wall requires energy. Ion tracks decrease this energy. Therfore the domain density can be increased.
Left: Ion irradiation (circle) increases the domain density. Right: Domain walls cross preferentially through ion tracks. In this way the total energy is minimized.
This work was initiated by J.P. Krumme, Philips Research Center, Hamburg.