Antiferroelectric correlation in relaxor Pb(In_1/2Nb_1/2)O₃ and ferroelectric correlation in antiferroelectric Pb(In_1/2Nb_1/2)O₃

抄録

Pb(In_1/2Nb_1/2)O₃ (PIN) can be antiferroelectric (AFE), ferroelectric (FE) or a relaxor depending upon the perovskite B-site randomness. This is characterized by measurements of dielectric response, which shows behavior that is usually clearly in one of those three classes. In contrast, x-ray scattering studies suggest the presence of AFE correlation in the relaxor state and FE in AFE state. Weak phonon softening at zone boundary in relaxor state shows that the AFE correlation intrinsically exists in PIN, as does the corresponding elastic scattering at (h/2 k/2 0), while weak diffuse scattering around 333 Bragg reflection appears in AFE state suggesting FE correlation. These results will support our previous speculation that the AFE and FE correlations coexist in PIN (K. Ohwada et al., Phys, Rev. B77 094136 (2008)). Such a coexistence or competition is widely seen in the perovskite relaxor and the coexistence of FE and AFE correlations is essential for generating relaxor state.