High magnetic permeability in Ni-Fe alloys

Abstract

Some of the magnetic properties of complex Ni-Fe alloys containing about 80% Ni can be explained by considering the effect of the filling of the 3d vacancies of the nickel atoms by the outermost electrons of the added non-ferromagnetic element. Some new data on high initial permeability alloys are presented which suggest explanations for: (i) the decrease in saturation induction with additions of molybdenum and copper; (ii) the narrow region of alloy compositions in which high initial permeabilities are found; (iii) the nature of the ordering process which influences the initial permeability; (iv) the effects of additions of molybdenum and copper on the ordering process. Changes of initial losses with heat treatment are also considered. A method for calculating the optimum composition for high initial permeability is given, with empirical data from which the optimum final heat treatment can be derived.