P. S. Spoor
M. J. McKenna
J. D. Maynard
Penn State Univ., University Park, PA 16802
The study of acoustic waves in a solid can reveal many of its fundamental properties, such as the Debye temperature, the second derivatives of the free energy, and the strength of the electron--phonon coupling---but only if a specimen can be considered a single crystal with a minimum of defects and impurities. Such specimens tend to be extremely small and fragile, especially for newly discovered materials. Often, as the case with the high-temperature copper oxide superconductors, the samples can only be grown as wafers, typically 200x200x40 (mu)m in size. These extremely small sizes and the ``plate'' proportions complicate the resonant ultrasound technique because stress on the sample from the transducers is more of a concern; second, only the ``plate'' modes, which have no dependence on the thin dimension, can be excited, and the overtones are widely spaced in frequency, so frequency-dependent mechanisms have to be considered; for example, measurements of the attenuation are of particular interest in high T[sub c] materials. Applications to high T[sub c] and TiB[sub 2] crystals will be discussed. [Work supported by NSF Grant No. DMR-9000549 and by the Office of Naval Research.]