Strain driven magnetism in thin films of LaCoO3

TL;DR

This study uses first-principles calculations to show how substrate-induced lattice strain causes a spin state transition in LaCoO3 thin films, stabilizing ferromagnetism and explaining temperature-dependent spectral features.

Contribution

It reveals that substrate strain alone induces a spin state transition and ferromagnetism in LaCoO3 films, clarifying previous uncertainties about the origin of these effects.

Findings

Lattice strain causes a spin state transition in LaCoO3.

Intermediate spin state stabilizes ferromagnetism.

Temperature dependence of X-ray spectra explained by strain effects.

Abstract

The electronic structure of epitaxial films on LaCoO3(LCO) has been studied within first principle electronic structure calculations. A spin state transition is found to take place as a function of lattice strain which freezes in the intermediate spin state for non zero strain. In contrast to earlier speculations this is found to arise from substrate strain alone and angle variations are small. The intermediate spin state also stabilizes ferromagnetism in the ground state. The anomalous temperature dependence of the X-ray absorption spectra for films of LCO on LCO and its absence in films of LCO on (LaAlO_{3})_{0.3}(SrAlTaO_{6})_{0.7}$(LSAT) is also explained.