Irradiation-induced decay of magnetic permeability of metglas 2605S-3 and mumetal

Abstract

In order to compare the radiation resistance of amorphous and crystalline magnetic alloys, samples of commercial high-permeability alloys were irradiated with high-energy neutrons near the beam stop at LAMPF. Both crystalline and amorphous alloys showed a decrease of permeability with increasing fluence, while control samples held at the same temperature showed no change of permeability. Samples prepared from Mumetal and the amorphous alloy, Metglas 2605S-3 were tested. The permeability of the Metglas 2605S-3 sample showed a rate of decrease at least a factor of ten slower than for the crystalline alloys. The permeability decrease as a function of fluence for both alloys can be separated into two distinct stages. The first stage is thought to be due to short-range ordering which occurs at an enhanced rate due to the excess point defects produced by the irradiation. The second stage is believed to be caused by pinning of domain walls on defect clusters produced in the collision cascade.