Thermal conductivity of fullerite C-60 crystals at low temperatures

The thermal conductivity kappa of extended crystals of fullerite C-60 with transverse dimensions L of the order of a few millimeters is measured at lo w temperatures (down to 0.6 K). It is found that in the range from 7 to 0.6 K the temperature dependence of the thermal conductivity of the better of the samples is close to cubic, kappa (T)similar toT(3), and the effective p honon mean free path estimated from the measured thermal conductivity and t he published value of the specific heat of fullerite [J. R. Olson , Science 259, 1145 (1993)] has a value (l(p)approximate to0.6 mum) that is practica lly independent of temperature and much less than L, i.e., the phonon mean free path is limited by strong scattering on defects in the bulk of the sam ple. (C) 2001 American Institute of Physics.