Ferromagnetism of Organic Radical Crystals of Tempo Derivatives

Several TEMPO-based radicals were found to be bulk ferromagnets with T C of 0.2–0.4 K, as indicated by the measurements of ac magnetic susceptibilities and magnetization curves. On the basis of the X-ray crystal structure analysis, a possible mechanism of ferromagnetic interactions between neighboring N-O sites is proposed, in which the methyl or methylene groups play a role of ferromagnetic exchange couplers. New organic ferromagnets, 4-(p-methylthiobenzylideneamino)-TEMPO, 4-(benzylamino)-TEMPO, and 4-(hydroxyimino)-TEMPO as well as several metamagnets are reported.