The nucleation of domains in permalloy using low intensity ultrasound

Polycrystalline films of 60-40 NiFe prepared under specified conditions exhibit a behaviour which is at present being explored for possible applications in medical ultrasound diagnostic systems. The magnetization in a chosen area of the film can be switched by exposure to ultrasound. This switching proceeds via the nucleation of domains of ´reverse´ magnetization. These nucleation centers have not yet been identified in terms of a physical model and it is the aim of this paper to go some way in this direction.