Measurement of third-order elastic moduli of yttrium iron garnet

The third-order elastic moduli of yttrium iron garnet (YIG) have been determined from measurements of ultrasonic velocity. A pulsed ultrasonic system which uses a phase comparison principle to measure velocity versus applied stress is described. In units of 1012 dyn/cm2 and for 28°C, the third-order moduli are: C111=-23.3±0.8 C 112=-7.17±0.6 C123=-0.33±1.3 C 144=-1.48±0.29 C155=-3.06±0.14 C 456=-0.97±0.16. Thermodynamic definitions for the moduli [K. Brugger, Phys. Rev. 133, A1611 (1964)] have been used. © 1966 The American Institute of Physics.