Mu-metal

[4] The annealing alters the material's crystal structure, aligning the grains and removing some impurities, especially carbon, which obstruct the free motion of the magnetic domain boundaries.

Its higher saturation value allows it to handle stronger magnetic fields, reducing them to a lower level that can be shielded effectively by the inner mu-metal layers.

The low magnetostriction is critical for industrial applications, where variable stresses in thin films would otherwise cause a ruinously large variation in magnetic properties.

For example: Other materials with similar magnetic properties include Co-Netic, supermalloy, supermumetal, nilomag, sanbold, molybdenum permalloy, Sendust, M-1040, Hipernom, HyMu-80 and Amumetal.

Ceramic ferrites are used for similar purposes, and have even higher permeability at high frequencies, but are brittle and nearly non-conductive, so can only replace mu-metals where conductivity and pliability aren't required.

Telcon invented mu-metal to compete with permalloy, the first high-permeability alloy used for cable compensation, whose patent rights were held by competitor Western Electric.

In the 1930s this use for mu-metal declined, but by World War II many other uses were found in the electronics industry (particularly shielding for transformers and cathode-ray tubes), as well as the fuzes inside magnetic mines.