Room-Temperature Magnetic Bistability in Organic Radical Crystals

A large first-order magnetic phase transition in an organic radical, 1,3,5-trithia-2,4,6-triazapentalenyl, is described. The transition occurs with a wide thermal hysteresis loop over the temperature range 230 to 305 kelvin. The high-temperature phase is paramagnetic, and its structure consists of a uniform one-dimensional stacking of the radical. The low-temperature phase is diamagnetic because of strong dimerization along the stacking direction. The results may have applications in thermal sensors, switching units, and information storage media based on organic radical crystals.