Organic Magnets, J. S. Miller, CRC Handbook of Chemistry and Physics, 81th ed. 12-126 - 126-129 (2000).

Magnetic ordering, e. g., ferromagnetism, like superconductivity, is a property of a solid, not of an individual molecule or ion, and very rarely occurs for organic compounds. In contrast to superconductivity where all electron spins pair to form a perfect diamagnetic material, magnetic ordering requires unpaired electron spins; hence, superconductivity and ferromagnetism are mutually exclusive.

The vast majority of organic compounds are diamagnetic (i. e., all electron spins are paired) and a relative few possess unpaired electrons (designated by an arrow, h) and are paramagnetic (PM), i. e., they are in random directions. Very few organic solids, however, exhibit strong magnetic behavior, and magnetically order as ferromagnets (FO) with all spins aligned in the same direction. In some cases the spins align in the opposite direction and compensate and form an antiferromagnet (AF). In some cases these spins are not opposed to each other and do not compensate and lead a canted antiferromagnet or weak ferromagnet (WF). If the number of spins that align in one direction differ from the number of spins that align in the opposite direction, the spins cannot compensate and a ferrimagnet (FI) results. Metamagnets (MM) are antiferromagnets in which all the spin become aligned like a ferromagnet in an applied magnetic field. Above the ordering or critical temperature, Tc, all magnets are paramagnets (PM). Organic magnets all possess electron spins in p-orbitals, but may be in conjunction with metal ion based spins.