New High-T_c molecule-based Magnets – Magnetic Behavior of M^II(TCNE)₂…x(CH₂Cl₂) (M = Mn, Fe), M. A. Girtu, C. M. Wynn, C. R. Kmety, A. Y. Mishurov, J. Zhang, J. S. Miller, A. J. Epstein, Mol. Cryst., Liq. Cryst., 334, 539-548 (1999).

We report and review studies of new partially crystalline members of the high-T_c molecule-based magnets family, M(TCNE)₂… x(CH₂Cl₂), (M = Fe, Mn, TCNE = tetracyanoethylene). Remanent magnetization revealed high critical temperatures, T_c =97 K for M = Fe and 75 K for M = Mn. Hysteresis curves for the Fe compound, for 5 £ T £ 80 K, have a spin-flop shape, indicating ferrimagnetc behavior. Field-cooled and zero-field-cooled magnetization reveals magnetic irreversibilities below T_c for both compounds. Static and dynamic scaling analyses of the dc magnetization and ac susceptibility for M=Mn show a transition to a 3D ferrimagnetic state at T_c = 75 K, followed by a reentrant transition, to a spin glass state at T_g = 2.5 K. For M = Fe static scaling analyses are consistent with a high-T transition to a correlated sperimagnet, while below -20 K there is a crossover to sperimagnetic behavior.