Magnetic field creates parallel but opposing spins; varies with temperature WordNet 3.0 & Open English WordNet

In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins pointing in opposite directions. Wikipedia

A material property and type of magnetic ordering Wikipedia Disambiguation

A phenomenon, similar to ferromagnetism, in which magnetic domains line up in a regular pattern, but with neighbouring electron spins pointing in opposite directions; materials showing this effect are either ferrimagnetic or diamagnetic, and become paramagnetic above the Neel temperature. Wiktionary

A phenomenon, similar to ferromagnetism. Wiktionary (translation)