Emergent room temperature polar phase in CaTiO 3 nanoparticles and single crystals

Mariola O. Ramirez, Tom T.A. Lummen, Irene Carrasco, Eftihia Barnes, Ulrich Aschauer, Dagmara Stefanska, Arnab Sen Gupta, Carmen De Las Heras, Hirofumi Akamatsu, Martin Holt, Pablo Molina, Andrew Barnes, Ryan C. Haislmaier, Przemyslaw J. Deren, Carlos Prieto, Luisa E. Bausá, Nicola A. Spaldin, Venkatraman Gopalan

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Abstract

Polar instabilities are well known to be suppressed on scaling materials down to the nanoscale, when the electrostatic energy increase at surfaces exceeds lowering of the bulk polarization energy. Surprisingly, here we report an emergent low symmetry polar phase arising in nanoscale powders of CaTiO 3 , the original mineral named perovskite discovered in 1839 and considered nominally nonpolar at any finite temperature in the bulk. Using nonlinear optics and spectroscopy, X-ray diffraction, and microscopy studies, we discover a well-defined polar to non-polar transition at a T C = 350 K in these powders. The same polar phase is also seen as a surface layer in bulk CaTiO 3 single crystals, forming striking domains with in-plane polarization orientations. Density functional theory reveals that oxygen octahedral distortions in the surface layer lead to the stabilization of the observed monoclinic polar phase. These results reveal new ways of overcoming the scaling limits to polarization in perovskites.

Original languageEnglish
Article number011103
JournalAPL Materials
Volume7
Issue number1
DOIs
Publication statusPublished - Jan 1 2019

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)

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    Ramirez, M. O., Lummen, T. T. A., Carrasco, I., Barnes, E., Aschauer, U., Stefanska, D., Sen Gupta, A., De Las Heras, C., Akamatsu, H., Holt, M., Molina, P., Barnes, A., Haislmaier, R. C., Deren, P. J., Prieto, C., Bausá, L. E., Spaldin, N. A., & Gopalan, V. (2019). Emergent room temperature polar phase in CaTiO 3 nanoparticles and single crystals APL Materials, 7(1), [011103]. https://doi.org/10.1063/1.5078706