Search

If a material is very nearly isotropic, quantifying the residual anisotropy may be quite difficult using methods such as pulse superposition or neutron scattering, when only a small sample is available. However, resonant ultrasound spectroscopy using piezoelectric film transducers allows precise (

A brief review is given on some of the most interesting structural and electrical properties in the C60 fullerenes. The elasticity study is reported on for C60 single crystals of different lattice symmetries. The temperature dependence of the sound velocity in the fcc crystals shows a discontinuous jump corresponding to about 8% increase in the modulus at an orientational ordering transition temperature T=260 K. This large change in the elastic modulus indicates a drastic change in the interaction mechanism between the molecules. At T∼160 K, the sound velocity is observed to increase considerably accompanied by a profound peak in the sound attenuation whose position is frequency dependent. The 160 K anomaly is associated with relaxations of the C60 molecules to symmetry‐inequivalent orientations in response to the stress field with the characteristic relaxation frequency following an activated temperature dependence and coinciding with the measurement frequency of about 20 kHz around 160 K. In the monocli...