An ideally hard superconductor
is a type II superconductor
material with an infinite pinning force
(or critical current density
). In the external magnetic field it behaves like an ideal diamagnet
if the field is switched on when the material is in the superconducting state, so-called "zero field cooled" (ZFC) regime. In the field cooled (FC) regime, the ideally hard superconductor screens perfectly the change of the magnetic field rather than the magnetic field itself. The ideally hard superconductor is a good approximation for the melt-textured high temperature superconductors
(HTSC) used in large scale HTSC applications such as flywheels
, HTSC bearings, HTSC motors, etc.