Magnetic field insulators I was wondering if there is any way to stop the magnetic field, without having the insulator turned into magnet. Let me present this as a simple case, there is a magnet to the left and a piece of iron to the right, is there anything that I can put in between to stop the magnet from attracting the iron piece, provided that the insulator won't turn into a magnet as well?
I am open to all possibilities, any materials, electric fields or anything that can stop the magnet field without harming the magnet or the iron piece are welcome.
 A: Mu-metals are your best bet, though superconductors are useful in some situations.
You can think of mu-metals as redirecting the magnetic field, rather than neutralizing it.  So if you just have a flat piece mu-metal between the magnet and your piece of iron, you'll still get a reasonable amount of magnetic field -- it just had to "go farther" to get to the iron, so it will be weaker.  The usual design for shielding is a box enclosing whatever you want to shield.
Bringing a superconductor close to a magnet, on the other hand, will simply cancel out changes to the magnetic field inside the superconductor itself.  This is typically less useful for your problem, but it might be applicable for other applications you may need.  In particular, if you need fields eliminated from a cavity inside a material, this could function better than the mu-metal.
A: There is no material that can fully block a magnetic field, however there are materials that can re-route magnetic fields and can act as a "magnetic shield". These materials would typically be materials with a high magnetic permeability such as air. For more information, look here.
