Nick Mueller wrote:

It is. A bit. The right word to look for in wiki is susceptibility.

Just came to my mind:
Brass is halfway good for shielding magnetic fields, copper is better. But
you have to make a closed case. Not applicable in your case.
Materials out of my head, I might be wrong. Once made a shielding case for
measuring cellulars and researched a bit into that. In the case of radio
waves, things are a bit more complicated, because there are magnetic and
electric fields.

Mu-metal is best for shielding pure magnetic fields.

Nick