where Ncw is the density of unpaired spins on the C60 anions. A negative value for 0CW is anomalous, since dc magnetic susceptibility and magnetization measurements show that TDAE-C60 undergoes ferromagnetic ordering below a temperature of Tc = 16 K under ambient pressure (see Fig. 18.6). Furthermore, it has been shown that by cooling a TDAE-C60 sample through Tm in a magnetic field (9 T), a good fit to a Curie law is obtained from 4.3 K to 300 K, whereas zero-field cooled samples show com-
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