Magnet field in order to avoid too high especially in the process of transportation cause unnecessary trouble, star and magnetic industry suggest try with the following way: 1.
General masking method: sizzling shielding the magnetic field.
Magnetic shielding requires high permeability material, meet the requirements of the material is iron nickel alloy, this material has the very high magnetic permeability.
When you need to shield the magnetic field is very strong, only use single layer shielding materials, is not short of shielding requirements, will happen is saturated.
At this time, a method is to increase the thickness of the material.
More effective way is to use a combination of shielding, a shield on another screen, leave any wind gap between them.
Inside the air gap can fill any non magnetic permeability material, such as aluminum.
Composite shielding shielding effectiveness than single shield is much higher, so the composite shielding to magnetic field attenuation to very low levels.