Normally we use regular iron plates to block the magnetic field. Magnetic shielding requires high permeability material, and the material that meets this requirement is iron-nickel alloy, which has high permeability.
When the magnetic field that needs to be shielded is very strong, only use single layer shielding material, not to be unable to reach the shield requirement, it is to become saturated. At this point, one method is to increase the thickness of the material. But the more efficient way is to use composite shielding, placing a shield in the other, leaving a gap between them. The air gap can be filled with any non-permeable material, such as aluminum.
Composite shielding is much more efficient than a single shield, so combination shielding can attenuate the magnetic field to a low degree.