Effect of internal demagnetizing fields on the thermomagnetic writing process in MnAIGe films

Considerable structure has been found in the magnetization of spots written thermomagnetically on a film of MnAlGe by an impinging GaAs laser beam. Regions of the spot only 1 μm apart can exhibit strong, but opposing, remanence. We have investigated the effect of an external bias field on the behavior of different regions of the spot. From these experiments we show that the structure cannot be attributed either to local variations in film coercivity or to the fact that the magnetization reverses sign at a temperature well below the Curie point. These results support our previous conclusion that the effect is due to a demagnetizing field originating from within the spot during the writing process.