MAGNETIC-PROPERTIES OF POWDER AND CRYSTALLINE TDAE-C-60

Magnetic properties of a molecular soft ferromagnet TDAE-C-60 (TDAE; t etrakis(dimethylamino) ethylene) are studied by SQUID magnetometer bot h in powder and crystalline forms. In powder samples, a clear hysteres is between zero-field cooled (ZFC) and field cooled (FC) magnetization s was observed below about 10 K, consistent with our previous observat ion of a cusp in the temperature dependence of nonlinear ac susceptibi lity. In addition, an extremely slow relaxation phenomena of magnetiza tion and the stretched exponential type time-dependence was observed a t low temperatures. These characteristics are reminiscent of a ''spin- glass'' with the freezing temperature T-f at about 10 K, although the temperature dependence of magnetic moment at higher temperature above 10 K behaves like a ferromagnet with a transition temperatureT(C) simi lar to 16 K. On the other hand, an extremely sharp phase transition at similar to 16 K accompanied by a stepwise structure at about 10 K was observed in crystalline samples.