How Magnetic Shielding Works

May 2, 2017

MuShield’s high permeability magnetic shielding material commonly referred to as Mu Metal – meeting spec ASTM A753 – is a “soft” ferromagnetic magnetic shielding material that does not retain a macroscopic internal field after the removal of an external magnetizing field. Most of the materials that we work with are high permeability alloys that contain approximately:

  • 80% Nickel (Ni)
  • 20% Iron (Fe)
  • Small amounts of Molybdenum (Mo)

The material offers extremely high initial permeability and maximum permeability with minimum hysteresis loss, which is perfect for most magnetic shielding applications.

Ferromagnetism – which is the basic mechanism by which certain materials (such as iron) form permanent magnets, or are attracted to magnets – originates at the quantum level.

Ferromagnetic elements have a lowest energy e-orbital state that aligns the e-spins parallel, thus giving an intrinsic magnetic moment to the atom. The lowest microscopic energy state of an ensemble of atoms is with these magnetic moments aligned to produce a net magnetic field. Since maintaining an external magnetic field would require energy, the lowest macroscopic energy state requires that the atoms divide into domains about 1,000 atoms across, and that the magnetic orientation of these domains be randomized.

In the presence of an externally applied magnetic field, the domains magnetically realign to some degree and thus generate their own external field. The primary field continues to exist, but now the net field is the sum (or superposition) of the primary and induced field. The induced field must have an alignment of opposite polarity to the primary field (just like two bar magnets must align North to South and South to North), and the superposition of the two fields results in a lower observed field, and there you have magnetic shielding.

Are you still with us? (That was a mouthful…)

In short, Mu Metal was designed to serve as the best low frequency magnetic shielding material and we at MuShield have over 40 years experience designing and fabricating magnetic shields from it.

Do you have a need for a custom Mu Metal magnetic shield expertly fabricated by our experienced and talented team? Are you having magnetic interference problems and could benefit from a consultation with our engineering staff or a custom magnetic shield?

If you answered yes to either of these, contact us now at and let our team go to work for you. Interference be gone!

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