Antiferromagnetism is a form of magnetism in which the magnetic moments of neighbouring atoms are arranged anti-parallel.
As with ferromagnetism there are materials that show magnetic ordering below a critical temperature. Here, because of quantum phenomena, the atoms are arranged to form alternating magnetic moments with opposing directions. As a result, the material appears not to be magnetised despite the magnetic ordering within it.
The French scientist Louis Néel received the Nobel prize for Physics for his work on antiferromagnetism.