MAGNETIC HEAT-CAPACITY OF TDAE-C60

The heat capacity of TDAE-C60 (TDAE: tetrakis (dimethylamino)ethylene) was measured between 5 and 100 K using an adiabatic calorimeter. The magnetic phase transition was detected as a broad heat capacity peak a t 12.5 K. The enthalpy and entropy of transition are 0.43 kJ/mol and 3 4 J/K mol, respectively. Such a large value of the entropy of transiti on compared with 2R ln 2 = 11.5 J/K mol expected for a localized spin- 1/2 system probably reflects the multi-state of C60- due to dynamic Ja hn-Teller distortion in the high-temperature region above T(c).