Structural transitions and complex domain structures across a ferroelectric-to-antiferroelectric phase boundary in epitaxial Sm-doped BiFeO3 thin films

Abstract

We have investigated structural phase transitions across a ferroelectric-to-antiferroelectric phase boundary in epitaxial (001) oriented Bi(1−x)Sm(x)FeO3 thin films. For the Sm3+ concentration of 0.1<x<0.14, we observe short-range antiparallel cation displacements, verified by the appearance of localized 1/4 {011} weak reflections in the selected area electron diffraction patterns. At the critical composition of x=0.14, the system adopts a complex nanoscale domain mixture with appearance of 1/4 {011},1/2 {011}, 1/2 {010}, and 1/2 {111} reflections and an incommensurate phase bridging the rhombohedral and orthorhombic phases. For compositions 0.14<x<0.2, orientational twin domains coupled with antiphase oxygen octahedral tilts, identified by 1/2 {hkl} weak superstructure are observed. The above systematic changes in the microstructure as a function of Sm3+ doping are linked to the macroscopic functional properties.