Does this kind of magnetic sheild material exist?

[CARN0T]

Well, Broli,

I'll start off by saying I was wrong when I said--

Will the magnetic field change as the material goes to superconducting?-- I don't think so, since energy would be required and I don't see a source for that.  (I could be wrong on this point--somebody should check.)

Yep, I was wrong.  Checking on the Meissner effect, the magnetic field inside the material is "expelled" as it transitions to superconducting.  With this correction, it appears that I am incapable of thinking of a situation where a magnetic shield would pass a magnetic field originating inside the shell but not one from outside.

Wait a minute, maybe I was wrong again!  Let's look at that situation again--

Consider the magnet inside the shell above the transition, and the field passes through the shell.  Now, cool down and transition to the superconducting state.  The Meissner effect as stated only requires that the field be exluded from inside the material.  The material generates surface currents that cancel out the field within.  IF that's all it does, then the field outside didn't collapse, but is being maintained by the superconductor.

Okay, we know I am wrong at least once here.

Ernie Rogers