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Magnetic Shielding Material
Mu metal
Home / Mu metal / Suitable Shielding Materials for Magnets
Suitable Shielding Materials for Magnets January 2,2018.
During these years we’ve been asked many times that if our Mu Metal is able to shield a magnet. Unfortunately the answer has always been NO. Then have you ever wondered how a magnet can be shielded? Can a magnetic field be blocked so a magnet only pulls on one side? Or do you need to shield a sensitive device from magnetic fields?

There is an important point we have to be clear: magnetic shields can’t block a magnetic field. No material can stop the lines of flux from traveling from a magnet's North pole to it's South pole. The field can only be redirected.

If so, what material will work? Actually any ferromagnetic metal would work. In other words, anything containing iron, nickel or cobalt is OK. Most steels are ferromagnetic metals, and work well for a redirecting shield. Steel is commonly used because it's inexpensive and widely available.

Yet how about other metals? Are there any fancier shielding materials? Yes, there are some specialized materials specifically produced for magnetic shielding. The foremost of these is Mu Metal. Suppliers who provide magnetic shielding materials generally offer a version of Mu Metal, and some other proprietary alloys. Most of these have a high nickel content, with either 50% or 80% nickel.

Specialized magnetic shielding materials usually have a higher relative permeability, but a lower saturation point.

Permeability is the degree of magnetization of a material that responds linearly to an applied magnetic field. For shielding, Relative Permeability is the Permeability divided by the Permeability of free space, a constant. In more practical terms, Permeability is a measure of a material's ability to absorb magnetic flux. The higher the number, the better the shield. Low carbon steels have a Permeability of 1000 - 3000, while Mu Metal can have values as high as 300,000 - 400,000.

The saturation point is the flux density at which the material can not contain any more magnetic flux. Steel saturates around 22,000 Gauss, while Mu Metal saturates at about 8,000 Gauss. In lower flux density fields, such high permeability materials provide greater attenuation. In higher field densities, Mu Metal becomes saturated, and loses its effectiveness. In these cases, steel provides good attenuation and a much higher saturation threshold.

To sum up, which material is suitable for you depends on your specific shielding problem. For low field strength and sensitive electronics, Mu Metal Shielding can provide better shielding than steel. For many applications involving large and powerful neodymium magnets, the higher saturation point of steel works better.

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