Film Thickness Dependence of Ferroelectric Properties of (111)-Oriented Epitaxial Bi(Mg 1/2 Ti 1/2 )O 3 Films

The origin of the ferroelectricity of Bi(Mg 1/2 Ti 1/2 )O 3 films was investigated. Epitaxial Bi(Mg 1/2 Ti 1/2 )O 3 films with film thicknesses of 50 to 800 nm were grown on (111) c SrRuO 3 /(111)SrTiO 3 substrates by pulsed laser deposition. A Bi(Mg 1/2 Ti 1/2 )O 3 film was not strongly clamped from the substrate and identified to have rhombohedral symmetry with a = 0.398 nm and α= 89.8°, which was independent of film thickness within 100 to 800 nm. The relative dielectric constant, remanent polarization, and coercive field of the Bi(Mg 1/2 Ti 1/2 )O 3 films at room temperature were almost constant at about 250, 60 µC/cm 2 , and 240 kV/cm, respectively, for film thicknesses above 200 nm. These data suggest that Bi(Mg 1/2 Ti 1/2 )O 3 films are ferroelectric.