Mu Metal®

Mu Metal®

While Mu Metal does not block magnetic interference, it redirects the electromagnetic interference (EMI) into itself, which effectively protects the device. A wide range of industries utilize Mu Metal for this purpose, such as the electronic industry, for electric power transformers and photomultiplier tubes and the medical industry, for magnetic resonance imaging (MRI) equipment. Another application for Mu Metal is to prevent EMI from leaving an interfering device.

The effectiveness of Mu Metal in magnetic shielding is due to the way it is treated immediately following fabrication. Made in specialty metal mills, Mu Metal can be fabricated into foil, wire, enclosures or other objects that allow it to be used as a magnetic shield. For optimal magnetic shielding capabilities, Mu Metal can be formed into an enclosure that fits several other Mu Metal enclosures inside of it, allowing for better and better magnetic field reduction as the field passes through each enclosure. Once the Mu Metal enclosure is fabricated, it must be annealed in a magnetic field in a hydrogen atmosphere in order to allow for the best possible performance. Annealing should take place in a furnace with vigilant control of both the cooling rate and the annealing temperature. This will increase the magnetic permeability of the raw Mu Metal material and greatly improves its performance. This occurs because the annealing serves to change the crystalline structure of the Mu Metal by aligning the grains and removing any impurities that could potentially obstruct the movement of the magnetic domain boundaries. After the final annealing process, Mu Metal can have a maximum permeability of 450,000, which is extremely high especially in comparison to ordinary carbon steel, which has a relative permeability range in the several thousands.