Nonlinear relaxational ultrasonic absorption in metallic glasses

Abstract
We have developed a theory of intensity-dependent ultrasonic relaxational absorption in amorphous metals (metallic glasses). The relaxational absorption is due to the modulation of the interlevel spacing of the two-level systems by the periodic strain field of acoustic wave. The nonlinearity of the absorption coefficient appears to be essential if the amplitude of the modulation of the interlevel spacing exceeds kT