Measurement of the Anisotropy of the Lamb-Moessbauer Factor in euba2cu3o7

The lattice dynamics of high-Tc superconductor was studied by means of Moessbauer spectroscopy of the Eu151 in samples with oriented grains. Three samples were prepared: one oriented by means of 8 T magnetic field, another by means pressure; the third was left random. The orientation distribution function was determined be means of X-ray diffraction. By comparison of the absorption areas of the oriented samples with respect to the random one, the Lamb-Moessabuer ratio corresponding to the motions in c-direction and ab-plane was determined. This ratio turned out to be independent of the temperature and of value 0.25(5). This very small value can be explained only if a strongly anarmonicity is present, which mainly concerns the c-direction motion.