The Jahn-Teller effect, proposed by Jahn and Teller in 1937, describes how molecules or crystals with degenerate electronic orbitals can lower their total energy by distorting their structure. This distortion lifts the degeneracy, stabilizing certain orbitals that become occupied by electrons. While many materials exhibiting this effect have been found, the involvement of spin—the source of magnetism—has rarely been observed because magnetic ordering usually occurs at much lower temperatures than structural distortions caused by the Jahn-Teller effect.