The effects of various stresses on mumetal: 77 percent Ni-14 percent Fe-5 percent Cu-4 percent Mo

The effects of stress upon the magnetic properties of Mumetal have been studied in detail. The longitudinal Kerr effect has been used to study the domain patterns and the transverse Kerr effect used to obtain surface loops characteristic of the material. Bulk measurements were obtained by making standard bridge measurements of initial permeability. The effect of grinding has been studied using toroidal samples of thicknesses from 300 to 1620 μm. A possible method of estimating the depth of damage due to grinding by a) obtaining surface loops as layers of material have been successively chemically removed, and b) by "skin effect" testing, has been considered. The effect of simple tension on initial permeability has been examined for material with negative (-20 J/m³), zero and positive (+10 J/m³) values of anisotropy constant K1.