ZERO AND LOW-FIELD ESR OF THE MAGNETIC TRANSITION IN TDAE-C60

The electron spin resonance (ESR) spectra of tetrakis-dimethylamino-ethylene (TDAE)-C60 have been observed in the radiofrequency region and the resonant field - resonance frequency relation has been studied. At T(c) almost-equal-to 15 K a tremendous increase in intensity and a sudden line broadening occur as well as a shift of the center of the ESR line demonstrating the presence of a magnetic transition. A strong non-zero absorption is seen below T(c) at zero field supporting the above statement. The values of the local field are however much smaller than expected for the case that all C60- spins would order ferromagnetically.