Time dependent nonlinear response of a dipolar glass.

Linear susceptibility measurements obtained at frequencies between 10 sup 2 and 10 sup (12) Hz in KTa sub (1-x) Nb sub x O sub 3 revealed glasslike relaxations for x = 0.009 extrapolating to a transition temperature of 3K. In addition measurements of the nonlinear dielectric response obtained between 10 sup (-3) and 10 sup 5 Hz were undertaken to elucidate the appropriateness of spin glass models for this system. We find that the nonlinear polarization is a non-analytic function of electric field even at temperatures well above the linear susceptibility peak and at the lowest fields (4V/cm) available. The polarization response following application of a voltage step exhibits waiting time effects akin to those observed in spin glasses; but the dynamics is otherwise more complicated than predicted by existing theoretical models.