ATTENUATION OF LOW-FREQUENCY ACOUSTIC ENERGY IN BI-BASED SUPERCONDUCTORS

The attenuation of low-frequency acoustic energy in stripes of the low -temperature tetragonal phase of Bi-2212 ceramics is studied taking in to account the d(x2-y2)-symmetry of the superconducting order paramete r (SOP) and the dynamic analog of phase separation. The contribution t o the energy density of the strain-order parameter coupling leads to a finite value of attenuation in superconductors with a peculiar SOP. T he frequency and temperature dependences of attenuation are analyzed a nd compared with the available experimental results. It is shown that these data are an indirect evidence of the SOP symmetry: the d(x2-y2)- symmetry for the Bi-2212 phase and the s-symmetry for the Bi-2223 phas e. The existence of an ordered low-temperature state responsible for t he low-frequency attenuation peak and other anomalies in the propertie s of Bi-based ceramics in the temperature range 20-40 K is proposed. ( C) 1998 American Institute of Physics. [S1063-777X(98)01110-4]