insulation from magnetism?

Answer 1

What are you trying to shield from magnetism? Yourself? If you build a cage of fairly heavy steel mesh, that will do it. That's the principle upon which watch cases were eventually designed, because the early ones (mechanical) were susceptible to damage by magnets held near them. By surrounding the works with a steel case, the magnetism was diverted around them.

Answer 2

There are two opposite ways:

A) Shell made with high permeability material
(such as soft iron). Such shell will suck magnetic
field inside its walls and keep it there. Still some
residual magnetic filed will remain inside the shell.

B) Shell made of ideal diamagnetic.
Type I superconductors are perfect diamagnetics
and shiled 100% of magnetic filed. The filed simply
cannot penetrate them at all.

Answer 3

There are metals with very high relative permeabilities, called mu-metals, that can be formed into sheets and act as shields for DC magnetic fields and low frequency EM fields.

For high frequency EM fields, normal RF shielding techniques work quite well.

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