Hi Jones, Is it possible that you are confusing antiferromagnetic, which is a ferromagnetic material where the electron spins in alternating layers of atoms are in opposite directions with magnetic shielding such as is provided by superconductors. Antiferromagnetic to paramagnetic transitions provide only very small changes in mu. Antiferromagnetic to ferromagnetic or paramagnetic to ferromagnetic would provide large changes in mu and would therefore be suitable for magnetic gates.
George Holz Varitronics Systems 1924 US Hwy 22 East Bound Brook NJ 08805-1520
