Mu-metal
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Mu-metal, or μ-metal, is a soft nickel–iron ferromagnetic alloy with very high permeability, which is used for shielding sensitive electronic equipment against static or low-frequency magnetic fields.
Assortment of mu-metal shapes used in electronics, 1951
Five-layer mu-metal box. Each layer is about 5 mm thick. It reduces the effect of the Earth's magnetic field inside by a factor of 1500.
Mu-metal shields for cathode-ray tubes (CRTs) used in oscilloscopes, from a 1945 electronics magazine
Electrical steel
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Electrical steel is speciality steel used in the cores of electromagnetic devices such as electric motors, electric generators, and transformers because it reduces power loss. It is an iron alloy with
Polycrystalline structure of grain oriented electrical steel after coating has been removed.