Multiple strain-induced phase transitions in LaNiO3 thin films

TL;DR

This study investigates how strain influences phase transitions in LaNiO3 thin films, revealing new Raman modes and multiple strain-induced structural phases through combined experimental and computational approaches.

Contribution

It demonstrates the existence of multiple strain-driven structural transitions in LaNiO3 films, supported by Raman spectroscopy and first-principles simulations, highlighting strain's role in phase stability.

Findings

New Raman modes appear under strain, indicating symmetry reduction.

Different crystal symmetries are observed for tensile and compressive strains.

Simulations predict multiple stable phases under various strain conditions.

Abstract

Strain effects on epitaxial thin films of LaNiO3 grown on different single crystalline substrates are studied by Raman scattering and first-principles simulation. New Raman modes, not present in bulk or fully-relaxed films, appear under both compressive and tensile strains, indicating symmetry reductions. Interestingly, the Raman spectra and the underlying crystal symmetry for tensile and compressively strained films are different. Extensive mapping of LaNiO3 phase stability is addressed by simulations, showing that a variety of crystalline phases are indeed stabilized under strain which may impact the electronic orbital hierarchy. The calculated Raman frequencies reproduce the principal features of the experimental spectra, supporting the validity of the multiple strain-driven structural transitions predicted by the simulations.