Effects of mo content and baking temperature on permeability in Ni-Mo-Cu-Fe and Ni-Mo-Fe permalloys

The dependence of 60 Hz initial and maximum impedance permeabilities on the Mo content and baking temperature for both Cu-bearing and Cu-free permalloy strip was established, Each composition has its own optimum baking temperature resulting in the highest permeability. When Ni and/or Cu contents are fixed, higher Mo content results in lower optimum baking temperatures, Permeabilities fall rapidly when the baking temperatures are lower than 470 degrees C due to the formation of long range order (Ni3Fe). For a given Ni and/or Cu content, an optimum Mo content exists for the highest maximum permeability, As an example, the maximum permeability was as high as 466,000 in 0.071 mm (0.0028 in.) thick strip with an optimum composition (77Ni4.2Mo4.5Cu-Fe) after the cores were baked at 485 degrees C.