First-principles study of symmetry lowering and polarization in BaTiO3/SrTiO3 superlattices with in-plane expansion

Johnston, Karen and Huang, Xiangyang and Neaton, Jeffrey B. and Rabe, Karin M. (2005) First-principles study of symmetry lowering and polarization in BaTiO3/SrTiO3 superlattices with in-plane expansion. Physical Review B: Condensed Matter and Materials Physics, 71 (10). 100103(R). ISSN 1098-0121

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    Abstract

    The crystal structure and local spontaneous polarization of sBaTiO3dm/ sSrTiO3dn superlattices are calculated using first-principles density-functional theory. The in-plane lattice constant is constrained to be 1% larger than the SrTiO3 sSTd substrate to take into account the in-plane expansion observed in recent experiments. The symmetry is lowered to monoclinic space group Cm allowing for polarization along the f110g and f001g directions. The polarization component in the f110g direction is found to develop only in the SrTiO3 layers and falls to zero in the BaTiO3 sBTd layers, whereas the polarization in the f001g direction is approximately uniform throughout the superlattice. These findings are consistent with recent experimental data and firstprinciples results for epitaxially strained BT and ST.