Wall propagation by thermomagnetic writing in MnBi single crystal films

When a laser beam is focused to a spot on a MnBi single crystal or a polycrystalline MnBi film, a domain wall is nucleated which propagates from the heated spot by various mechanisms dependent on the direction of magnetization, the process of the crystal growth, and the effect of the adjacent crystal. The mechanism of the propagation can be interpreted by strip and bubble-domain theory. It is expected that the crystallographic and magnetic properties of films or crystals can be microscopically investigated by this heating method. The condition for stable writing according to bubble theory indicate that a stable spot can be written in a homogeneous and oriented MnBi film of thickness between 200 and 500 Å. This condition was experimentally confirmed.