Phonons and fractons in the vibration spectrum of the relaxor ferroelectric PbMg1/3Nb2/3O3

This paper describes the results of Raman and inelastic neutron-scattering studies for the PbME1/3Nb2/3O3 (PMN) relaxer ferroelectric. The comparative analysis of the low-frequency region of the vibrational spectrum has revea led the excitation at the frequency of the order of 50 cm(-1) which we rega rd as a fracton. In the generalized density of vibrational states this exci tation corresponds to the portion of the curve with the exponent (d) over t ilde = 1.5 at T = 77 K. Thus, we have observed a fracton in dielectric crys tals for the first time and therefore we believe that fractal ideology can be used to describe the physical properties of the PMN relaxer ferroelectri c. (C) 1999 Elsevier Science B.V. All rights reserved.