ASA 124th Meeting New Orleans 1992 October

3pPA6. Acoustic anomalies in the resonant ultrasound spectra of La[inf 2-x] Sr[sub x]CuO[sub 4].

John L. Sarrao

Ming Lei

Albert Migliori

Los Alamos Natl. Lab., M.S. K764, Los Alamos, NM 87545

Resonant ultrasound spectroscopy is a novel technique for the simultaneous determination of a solid's elastic moduli. Measurements of the resonant ultrasound spectra of single crystals of La[sub 2-x]Sr[sub x]CuO[sub 4] for several values of x are reported. Anomalies associated with the nonstoichiometric (x>0) doped superconductor have been observed. These anomalies indicate that the absence of short-wavelength translational invariance at the Brillouin-zone edge is being coupled into the zone center. Measurements of the stoichiometric (x=0) insulator will also be discussed. [This work was performed at Los Alamos National Laboratory under the auspices of the U.S. Department of Energy.]