Is the producing part correct? My understanding is that once cooled they reject magnetic fields, not produce them. According to wikipedia:

"The Meissner effect (or Meißner–Ochsenfeld effect) is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state when it is cooled below the critical temperature. This expulsion will repel a nearby magnet."

https://en.m.wikipedia.org/wiki/Meissner_effect