Phase transition and random-field induced domain wall response in quantum ferroelectrics SrTi¹⁸O₃: review and perspective

Abstract

The oxygen isotope exchange of 16 O by 18 O in SrTiO 3 causes a drastic change from paraelectric to ferroelectric, due to the suppression of quantum fluctuation. The phase transition and origin of the huge domain wall response were evaluated by dielectric, magnetic (NMR), and optical measurements (SHG, light scattering). The results obtained corroborate (1) smeared ferroelectric transition at T c due to quenched random field, (2) a quite large dielectric contribution from domain walls, (3) incomplete softening of the transverse optic mode, and (4) a large contribution from the relaxational mode to the phase transition. Quantitative explanations, given to individual results, may give hints to grasp the mechanism for the evolution of ferroelectricity, in which quantum fluctuation and random fields are dominant perturbations. Finally, some of the news studies on the SrTiO 3 were also introduced. q

Prospects and applications near ferroelectric quantum phase transitions: a key issues review

“…In the simplest models isotope subsitution softens the polar phonons, and there are several such theoretical discussions specific to STO [9,86,87,88]; here the key assumption is that the mass increases at constant stiffness. However we might also expect that a decrease in frequency increases the susceptibility and thus decreases the stiffness, leading to an increase in fluctuation amplitude.…”

Electronic structure, optical and dielectric properties of BaTiO3/CaTiO3/SrTiO3 ferroelectric superlattices from first-principles calculations

“…SrTiO 3 is a well-known perovskite material for quantum paraelectricity which has a very large dielectric constant with saturation at e = 20 000, associated with the softening of a long-wave length transverse optic phonon mode. 14 It can remain paraelectric until the temperature is below 0.3 K, while the ferroelectric polarization could easily occur with the balance of forces broken by the slight perturbation in the lattice structure, such as doping, strain and oxygen isotope substitution. 15 CaTiO 3 is also a well-known incipient ferroelectric with a dielectric constant of e = 180 in bulk crystals, 16 which shows no ferroelectric phase transition in spite of the intriguing dielectric constant behavior.…”

Effect of O2/Ar flow ratio and post-deposition annealing on the structural, optical and electrical characteristics of SrTiO3 thin films deposited by RF sputtering at room temperature

“…Single crystal, crystalline nanoparticle and polycrystalline thin film [13][14][15][16] structures for STO were noted in the literature. In crystalline form, STO thin films exhibit high dielectric constants of ~300, and moreover, they show paraelectric and ferroelectric characteristics even without permanent electric dipole [12,17]. Furthermore, in nanostructured thin film form they have ability to show multifunctional properties [18].…”