In-plane structural order of domain engineered La_0.7Sr_0.3MnO₃ thin films

Abstract

We present a detailed structural study of tensile-strained La_0.7Sr_0.3MnO₃ thin films. We use the substrate miscut to control the number of rhombohedral variants in the films and study the in-plane order and structural distortions. Using high-resolution X-ray diffraction, we demonstrate that step-edge induced lattice modulations occur in 4-variant films, whereas periodic twinning is the dominant in-plane order for 2-variant films. We show that the in-plane twinning angle is almost completely relaxed. However, the relaxation of shear strain by the out-of-plane twinning angle and the monoclinic distortion is only partial. Furthermore, the film thickness dependence of the domain width reveals that domain formation is a universal mechanism for shear strain relaxation. Finally, we show that the structural response to the transition from the paramagnetic to the ferromagnetic phase of La_0.7Sr_0.3MnO₃ at 345 K is smaller in 4-variant films compared to 2-variant films.

Keywords:

• perovskite
• domain engineering
• low symmetry
• shear strain relaxation
• thin films

Acknowledgements

This project was supported by the Norwegian Research Council under project number 10239707. Support from the Swedish Foundation for International Cooperation in Research and Higher Education (STINT) is acknowledged and R.M. acknowledges support from the Swedish Research Council (VR).