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.