Phase diagram of BiFeO3/LaFeO3 superlattices studied by x-ray diffraction experiments and first-principles calculations

Combining structural and functional measurements, we have mapped the phase diagram of BiFeO3/LaFeO3 superlattices grown by off-axis sputtering on (110)(o) DyScO3 substrates. The phase diagram displays three distinct regions as a function of BiFeO3 fraction, with a BiFeO3-like ferroelectric phase and a LaFeO3-like paraelectric phase at its extremities, and a complex intermediate region, as supported by first-principles calculations. This intermediate region shows unusual, mixed functional behavior, most likely due to competing phases driven by substitution with a same-size central ion and the specific boundary conditions imposed by the superlattice structure. In the BiFeO3 rich superlattices, scaling of the ferroelectric-to-paraelectric transition temperature with the BiFeO3 thickness could provide an alternate route for studying ferroelectric size effects in BiFeO3.