Magnetic domains and high permeability in Ni-Fe-Cu-Mo alloys

Abstract

Magnetic domains have been observed in material with composition close to 77% Ni-14% Fe-5% Cu-4% Mo for both vanishingly small and finite values of K1, the first anisotropy constant. An initial permeability of 70 × 103 was obtained. The domain structure was governed by random internal stresses in the material and no clear dependence on grain orientation or K1 was established. The application of tensile stress caused a reduction in permeability and an increase in eddy current loss. Bar-type domains are formed whose spacing diminishes with increasing stress. The results are shown to be in agreement with theory based on the μ* effect.