Strain-Dependence of the Structure and Ferroic Properties of Epitaxial NiTiO₃ Thin Films Grown on Different Substrates

Figure 1

(Color online) Predicted effect of in-plane strain on NiTiO₃ exerted using epitaxy. (a) Schematic epitaxial phase diagram of NiTiO₃ strained from 6% (in-plane compression) to 2.5% (in-plane tension). Regions with polar/ferroelectric (FE) and ferromagnetic (FM) behavior are shown. (b) Lattice parameter (in-plane) versus strain from mismatch for the three substrates used in this study. (c) Crystal structure of unstrained bulk NiTiO₃ in the desired R3c structure. Grey octahedra: NiO₆, blue octahedra: TiO₆. (d) Schematic of the in-plane straining (compression/expansion) of thin-film NiTiO₃ on the substrate (here, the structure of the LiNbO₃ substrate is shown, green octahedra are NbO₆, blue octahedra are LiO₆).