The Meissner Effect is the name given to the phenomenon of a material expelling all magnetic fields when it becomes superconducting.  Some materials can become superconducting by being super-cooled by something like liquid nitrogen (−195 °C or -320 °F).  The result is that a permanent magnet will levitate over the superconducting material!

The Physics Club at the University of Windsor purchased a Meissner effect demo to bring to outreach events.  The small silvery magnet you see in the video below is a neodymium magnet, a rare-earth metal with strong magnetic properties.  The black superconducting material is yttrium-based and is often used in demos because of it’s relatively high temperature superconductivity.

The magnet’s field extends beyond it’s physical boundary, and under normal conditions the field is allowed to penetrate inside the black material.  Once the liquid nitrogen is poured over it, it becomes super conducting and pushes all of the magnetic field out – it looks as if the magnet is being repelled.  Check it out!