Dynamic observation of thermomagnetic writing on MnBi films

Thermomagnetic writing on MnBi films was studied by dynamic observation on a change in a magnetization state using a two-beam method. As a writing laser beam increased in pulse duration, four writing characteristics were successively observed: I) nonwritable, II) writable without the first order phase transition, III) writable with the transition, and IV) decomposed. Observation of a nonmagnetic state in a writing cycle in II) revealed that the thermomagnetic writing is the extrapolated Curie point writing. The domain expansion phenomena observed in a writing cycle in II) are discussed based on a domain theory.