Long-Time Relaxation of the Dielectric Response in Lead Magnoniobate

We measured the time dependencies of the dielectric permittivity of a single crystal lead magnoniobate in the zero-field–cooled regime. The logarithmic decay of the dielectric response was observed in the glassy phase. We measured the time $\tau$ from the moment of the field application for the phase transition from the glasslike to the field-induced ferroelectric state to take place, at temperatures below 220 K. The transition is accompanied by the emerging of the even harmonics of the permittivity. It is shown that $\ln \tau$ depends linearly on both the inverse temperature and the inverse applied field strength.