Mu-metal is a nickel-iron alloy (approximately 75% nickel, 15% iron, plus copper and molybdenum) that has very high magnetic permeability. The high permeability makes mu-metal very effective at screening static or low-frequency magnetic fields, which cannot be attenuated by other methods. The name came from the Greek letter mu (μ) which represents permeability.
Mu-metal can have relative permeabilities of 80,000-100,000 compared to several thousa...
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Mu-metal is a nickel-iron alloy (approximately 75% nickel, 15% iron, plus copper and molybdenum) that has very high magnetic permeability. The high permeability makes mu-metal very effective at screening static or low-frequency magnetic fields, which cannot be attenuated by other methods. The name came from the Greek letter mu (μ) which represents permeability.
Mu-metal can have relative permeabilities of 80,000-100,000 compared to several thousand for ordinary steel. In addition it has low coercivity and magnetostriction resulting in low hysteresis loss. Its magnetic properties are no better than other high permeability alloys such as Permalloy, but it is more ductile and workable.
Mu-metal objects require heat treatment after they are in final form — annealing in a magnetic field in hydrogen atmosphere, which reportedly increases the magnetic permeability about 40 times. The annealing alters the material's crystal structure, aligning the grains and removing some impurities,...
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