Octahedral rotation patterns in strained EuFeO3 and other Pbnm perovskite films: Implications for hybrid improper ferroelectricity

• Published in: Physical review. B 2016-07, Vol.94 (2)
• Main Authors: Choquette, A. K., Smith, C. R., Sichel-Tissot, R. J., Moon, E. J., Scafetta, M. D., Di Gennaro, E., Miletto Granozio, F., Karapetrova, E., May, S. J.
• Format: Article
• Language: English
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.94.024105

We report the relationship between epitaxial strain and the crystallographic orientation of the in-phase rotation axis and A-site displacements in Pbnm-type perovskite films. Synchrotron diffraction measurements of EuFeO3 films under strain states ranging from 2% compressive to 0.9% tensile on cubic or rhombohedral substrates exhibit a combination of a(-)a(+)c(-) and a(+)a(-)c(-) rotational patterns. We compare the EuFeO3 behavior with previously reported experimental and theoretical work on strained Pbnm-type films on nonorthorhombic substrates, as well as additional measurements from LaGaO3, LaFeO3, and Eu0.7Sr0.3MnO3 films on SrTiO3. Compiling the results from various material systems reveals a general strain dependence in which compressive strain strongly favors a(-)a(+)c(-) and a(+)a(-)c(-) rotation patterns and tensile strain weakly favors a(-)a(-)c(+) structures. In contrast, EuFeO3 films grown on Pbnm-type GdScO3 under 2.3% tensile strain take on a uniform a(-)a(+)c(-) rotation pattern imprinted from the substrate, despite strain considerations that favor the a(-)a(-)c(+) pattern. These results point to the use of substrate imprinting as a more robust route than strain for tuning the crystallographic orientations of the octahedral rotations and A-site displacements needed to realize rotation-induced hybrid improper ferroelectricity in oxide heterostructures.