If there is coupling between the individual magnetic dipole moments of a paramagnetic sample, spontaneous ordering of the moments will occur at low temperatures.
If this ordering results in an electronic ground state in which the moments are aligned in the same direction (parallel), the substance is said to be ferromagnetic. This is the most familiar form of magnetism, associated with elements such as iron, cobalt, and nickel.
If the ordering results in an electronic ground state in which the moments are aligned in opposite directions, the substance is said to be antiferromagnetic.
