Abstract
The deformation of Heusler alloys during ball milling resulted in a drastic decrease in the crystallite size to a nanometer level. Nanocrystalline Heusler alloys with a disordered bcc structure were obtained by mechanical milling. This was accompanied by the disappearance of ferromagnetism. These nanocrystalline states were stable up to 523 K and ferromagnetism appeared after annealing at around 413 K. The nanocrystalline state with a L21 type structure was obtained by annealing at around 473 K. The nanocrystalline state lost stability and recrystallized with a D03 type structure when annealed at 573 K. The ferromagnetism almost disappeared in the powders after annealing at 573 K. In the recrystallized state, an increase in magnetization was observed with increasing annealing temperature. This came from the increase in the long range order parameter for the L21 type structure at room temperature.
