Two types of superconductors
Type-I superconductors are characterised by a total so-called Meissner effect. This means that the superconductor completely expels a magnetic field. If the magnetic field becomes too strong, the superconductive property disappears abruptly. But there are other superconductors, often alloys, in which the Meissner effect is not total. Here a surrounding magnetic field can intrude partly and the materials can retain their superconductive property even in very strong magnetic fields.

It takes two
If electrons and ³He atoms are to condense into a superfluid liquid, they must first pair up. This can take place in two ways concerning the particles’ magnetic properties, their so-called spin. This is described with an arrow – a compass needle. The spins are either opposite, in which case they counteract each other (electrons in a superconductor) or in the same direction so that they reinforce each other (³He atoms in a superfluid). In the latter case the superfluid can have magnetic properties.