Two-step phase changes in cubic relaxor ferroelectrics

The field-driven conversion between the zero-field-cooled frozen relaxor state and a ferroelectric state of several cubic relaxors is found to occur in at least two distinct steps, after a period of creep, as a function of time. The relaxation of this state back to a relaxor state under warming in zero field also occurs via two or more sharp steps, in contrast to a one-step relaxation of the ferroelectric state formed by field-cooling. An intermediate state can be trapped by interrupting the polarization. Giant pyroelectric noise appears in some of the non-equilibrium regimes. It is suggested that two coupled types of order, one ferroelectric and the other glassy, may be required to account for these data.