Type-I superconductor

Type of superconductor with a single critical magnetic field

The interior of a bulk superconductor cannot be penetrated by a weak magnetic field, a phenomenon known as the Meissner effect. When the applied magnetic field becomes too large, superconductivity breaks down. Superconductors can be divided into two types according to how this breakdown occurs.

From Wikipedia, under CC BY-SA. More on occurri.