We start with a single crystal sapphire wafer and coat it with a thin (~1µm thick) ceramic material called yttrium barium copper oxide (YBa2Cu3O7-x ). The ceramic layer has no interesting magnetic or electrical properties at room temperature. However, when cooled below -185ºC (-301ºF) the material becomes a superconductor. It conducts electricity without resistance, with no energy loss. Zero.
Superconductivity and magnetic field do not like each other. When possible, the superconductor will expel all magnetic fields from inside. This is the Meissner effect. In our case, since the superconductor is extremely thin, the magnetic field DOES penetrate. However, it does that in discrete quantities (this is quantum physics after all! ) called flux tubes (or fluxons).
Inside each magnetic flux tube superconductivity is locally destroyed. The superconductor will try to keep the magnetic tubes pinned in weak areas (e.g. grain boundaries). Any spatial movement of the superconductor will cause the flux tubes to move. In order to prevent that the superconductor remains “locked” in midair. For more details see here.