Critical temperatures of 70%Pb(Mg_1/3Nb_2/3)O ₃-30%PbTiO₃ thin films investigated by dielectric, ferroelectric, and structural measurements

The authors have investigated the temperature dependence of the ferroelectric, dielectric, and structural properties of 70%Pb(Mg _1/3Nb_2/3)O₃-30%PbTiO₃ thin films. Two critical temperatures were evidenced. The first one occurring around 410 K corresponds to the bulk paraelectric-ferroelectric phase transition and the second one around 200 K is rather related to a self-arrangement of small domains into macrodomains in order to minimize elastic energies. A multiscale domainlike structure is induced and the temperature evolution of such complex structure can be revealed through pronounced changes occurring in the nonlinear dielectric susceptibility.