Jqc

[18.36]

°C-centered monoclinic structure (see Fig. 8.16). Values given in this table are for room temperature and values given in §8.7.3 pertain to 11 K [18.45].

°C-centered monoclinic structure (see Fig. 8.16). Values given in this table are for room temperature and values given in §8.7.3 pertain to 11 K [18.45].

dependent ESR [18.36], NMR [18.42], and /xSR [18.42] linewidth studies. The lower value of Tm for TDAE-C60 relative to C60 (for which 701 = 261 K) can be understood in terms of the hindered rotation of the C60 molecules to which the bulky TDAE groups are attached (see §8.7.3). The correlation between the magnetic properties with the orientational molecular ordering was established by showing large differences in the measured susceptibility \'(T) and x"(T) below 20 K for TDAE-C60 samples slowly cooled through Tm and samples that had been quenched from 300 K to 30 K [18.36], Increased orientational ordering by slow cooling through Tm resulted in a sharper onset of the magnetization, a higher value of Tc, and a lower internal dissipation than for the quenched sample. Further confirmation for the correlation between orientational molecular ordering and spin ordering was provided by ESR experiments on samples cooled to 4 K in an external magnetic field of 9 T, where Tc was found to increase from 16 K to 28 K [18.36]. When a TDAE-C60 sample, which had been previously cooled to 4 K in a 9 T magnetic field, was subsequently heated above T01, the sample lost its memory of prior low-temperature molecular ordering.

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