Andre Geim demonstrated that the "anti" variety of this effect may be more common than the normal variety, and type II superconductors display a mixed variety of this effect.  It was first observed by its namesake discoverer in 1933 while cooling tin crystals to 3.72 K.  As the crystals approached the critical temperature, they began expelling the 
Andre Geim demonstrated that the "anti" variety of this effect may be more common than the normal variety, and type II superconductors display a mixed variety of this effect.  It was first observed by its namesake discoverer in 1933 while cooling tin crystals to 3.72 K.  As the crystals approached the critical temperature, they began expelling the earth's magnetic field from the interior, indicating the material had become perfectly diamagnetic.  FTP, identify this effect that demonstrates the falling off of the magnetic flux as a material becomes superconductive.
Andre Geim demonstrated that the "anti" variety of this effect may be more common than the normal variety, and type II superconductors display a mixed variety of this effect.  
Meissner effect