|MadSci Network: Physics|
Hi, The only material that actually blocks a DC magnetic field is a superconductor. That requires extreme cold and very special materials. The other way to "block" magnetic fields is to cancel them out by moving an easily magnetized body like a sheet of iron close to the point you want to shield. The best way to do it is to put a soft iron box around what you want to shield. That is not a perfect shield but will reduce the field perhaps a factor of 100 or more depending on the details. There is no way that I know of to shield a magnetic field with a body that does not react to the field.
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