over to the ordered magnetic state tend to be high, since interactions between spin centers is strong. Molecule-based magnets, however, have spin bearing units on molecular entities, often with highly directional bonding. In some cases, chemical bonding is restricted to one dimension (chains). Thus, interactions between spin centers are also limited to one dimension, and ordering temperatures are much lower than metal/alloy-type magnets. Also, large parts of the magnetic material are essentially diamagnetic, and contribute nothing to the net magnetic moment. Applications In 2015 oxo-dimeric Fe(salen)-based magnets ("anticancer nanomagnets") in a water suspension were shown to demonstrate intrinsic room temperature ferromagnetic behavior, as well as antitumor activity, with possible medical applications in chemotherapy, magnetic drug delivery, magnetic resonance imaging (MRI), and magnetic field-induced local hyperthermia therapy. Background Molecule-based magnets comprise a class of materials which differ from conventional magnets in one of several ways. Most traditional magnetic materials are comprised purely of metals (Fe, Co, Ni) or metal oxides (CrO2) in which the unpaired electrons spins that contribute to the net magnetic moment reside only on metal atoms in d- or f-type orbitals. In molecule-based magnets, the structural building blocks are molecular in nature. These building blocks are either purely organic molecules, coordination compounds or a combination of both. In this case, the unpaired electrons may reside in d or f orbitals on isolated metal atoms, but may also reside in highly localized s and p orbitals as well on the purely organic species. Like conventional magnets, they may be classified as hard or soft, depending on the magnitude of the coercive field. Another distinguishing feature is that molecule-based magnets are prepared via low-temperature solution-based techniques, versus high-temperature metallurgical processing or electroplating (in the case of magnetic thin films). This enables a chemical tailoring of the molecular building blocks to tune the magnetic properties. Specific materials include purely organic magnets made of organic radicals for example p-nitrophenyl nitronyl nitroxides, decamethylferrocenium tetracyanoethenide, mixed coordination compounds with bridging organic radicals, Prussian blue related compounds, and charge-transfer complexes. Molecule-based magnets derive their net moment from the cooperative effect of the spin-bearing molecular entities, and can display bulk ferromagnetic and ferrimagnetic behavior with a true critical temperature. In this regard, they are contrasted with single-molecule magnets, which are essentially superparamagnets (displaying a blocking temperature versus a true critical temperature). This critical temperature represents the point at which the materials switches from a simple paramagnet