Ultrasonic measurements of the C₁₁elastic constant in a Rb_1-x(NH₄)_xH₂PO₄glass

Ultrasonic measurements of the C11elastic constant in a mixed ferroantiferro-electric single crystal Rb1-x(NH4)xH2PO4with x = 0.35 are presented. The system undergoes a transition to a glassy state at low temperatures. The measurements are analysed assuming quadratic coupling between strain and the local polarization fluctuations, and are compared to results obtained with Brillouin scattering. © 1988 IOP Publishing Ltd.