Colorado State University

Resonant Ultrasound

Ultrasonic spectroscopy has been used for many years at Colorado State University as a sensitive probe of condensed matter. As discussed in the book by Truell, Elbaum and Chick, ultrasonic spectroscopy is defined as the measurement of attenuation and velocity of ultrasonic waves in materials. The current focus is on a powerful new technique called Resonant Ultrasound Spectroscopy. RUS involves the excitation of the vibrational eigenmodes of a small sample, usually in the shape of a rectangular parallelepiped. Calculated vibrational eigenmodes for a rectangular parellepiped are illustrated at the top of this page. A RUS spectrum of a single sample of mm dimensions yields the full set of elastic constants, even for relatively low-symmetry materials. In addition, the Qs of the resonances provide information about slow dynamic process difficult to investigate with many other techniques. Whereas conventional ultrasonic techniques rely on the propagation of plane waves with resultant sample dimensions usually of the order of centimeters, RUS is based on the measurement of the vibrational eigenmodes of samples of well-defined shapes, usually parallelepipeds or spheres. RUS has several features which make it especially attractive for condensed matter physics studies.

1. Rather small samples may be used. Reliable measurements are possible on samples of mm dimensions, or smaller.
2. There is no bond between the transducer and the specimen. The result is at temperature dependent data become much easier to acquire because the problem of differential thermal contraction of the bond, specimen, and transducer is avoided.
3. All the elastic constants, even for low-symmetry materials, can be determined from one spectrum on one specimen.
4. Typical millimeter-size samples result in resonant frequencies of a few hundred kHz to a few MHz. As a result, RUS is sensitive to dynamic processes in this frequency range, a range difficult to access by many other techniques.

Additonial information may be found in the following articles.

R. Truell, C. Elbaum, and B.B. Chick. Ultrasonic methods in solid state physics. Academic Press, 1969.

A. Migliori, J. L. Sarrao, W. M. Visscher, T.M. Bell, M. Lei, Z. Fisk, and R. G. Leisure, “Resonant Ultrasound Spectroscopic Techniques for Measurement of the Elastic Moduli of Solids,” Physica B 183, 1 (1993).

J. Maynard “Resonant Ultrasound Spectroscopy,” Phys Today 49, 26-31 (Jan 1996).

A. Migliori and J. L. Sarrao, Resonant Ultrasound Spectroscopy (Wiley, New York, 1997).

R.G. Leisure and F.A. Willis, “Resonant Ultrasound Spectroscopy” J. Phys.: Condens. Matter 9, 6001 (1997).

A. MIglior and J.D. Maynard, “Implementatioon of a Modern Resonant Ultrasound Spectroscopy System for the Measurement of the Elastic Moduli of Small Solid Specimens” Rev. Sci. Instrum. 76, 121303 (2005).