Fig. 1: DFT predicted stabilities of the AFE and FiE phases.

Total energies of the FiE and AFE phases as a function of epitaxial biaxial strains in (100) plane (a) and in (001) plane (b). The insets show the schematic diagram of applied biaxial strain, where both FiE and AFE phase have their dipole ordering in (001) plane along [110] or [1\(\bar{1}\)0] direction.