All commercially available magnetic shielding materials are
ferromagnetic. This means they are attracted by a magnet just like iron
or steel. Ferromagnetic materials are necessary because shields work by
pulling the magnetic field towards them and away from what needs to be
shielded. The magnetic field will actually become concentrated within
the shield itself, but the field will still exist.
If two magnets are close enough together to attract each other
and a ferromagnetic material is placed between them both magnets are now
attracted to the shield. The net effect is that both magnets are still
being attracted in the same direction prior to the shield being put in
place.
Now turn one of the magnets around so they are repelling each
other and then place ferromagnetic material between them. Again the
magnets are attracted to the shield and will stick to it. With a thick
enough piece of material the poles may actually be directed facing each
other. With a thinner piece the magnets will be offset from each other,
but will still stick to the shield.
