Pressure-induced enhancement of T-c in a genuine organic bulk-ferromagnet

Few genuine organic bulk-ferromagnets have been synthesized until now, but their transition temperatures (T-c) do not exceed 1.5 K. The representative organic bulk-ferromagnets such as beta-phase p-NPNN (T-c = 0.61 K) and p-C l-C6H5CH=N=TEMPO (T-c = 0.28 K) show a ferro-to-antiferromagnetic transitio n under pressure. In 2,5-DFPNN (T-c = 0.48 K), however, we find that ferrom agnetism is stable even under pressure, and T-c increases with pressure. Th is result gives us a clue for realizing the high-temperature organic bulk-f erromagnet. (C) 2000 Elsevier Science B.V. All rights reserved.