Suppression of spin-state transition in epitaxially strained LaCoO_{3}

TL;DR

This study reveals that epitaxial strain in LaCoO₃ thin films suppresses the spin-state transition, maintaining a constant spin state and enabling ferromagnetic order, unlike polycrystalline films which undergo spectral changes and remain paramagnetic.

Contribution

It demonstrates that epitaxial strain inhibits the temperature-induced spin-state transition in LaCoO₃ thin films, which is crucial for understanding their magnetic properties.

Findings

Epitaxial LaCoO₃ films show no significant spectral changes with temperature.

Epitaxial strain prevents the low-spin state population at low temperatures.

Epitaxial LaCoO₃ exhibits ferromagnetic order with T_c = 85 K.

Abstract

Epitaxial thin films of LaCoO_{3} (E-LCO) exhibit ferromagnetic order with a transition temperature T_c = 85 K, while polycrystalline thin LaCoO_{3} films (P-LCO) remain paramagnetic. The temperature-dependent spin-state structure for both E-LCO and P-LCO was studied by x-ray absorption spectroscopy at the Co L_{2,3} and O K edges. Considerable spectral redistributions over temperature are observed for P-LCO. The spectra for E-LCO, on the other hand, do not show any significant changes for temperatures between 30 K and 450 K at both edges, indicating that the spin state remains constant and that the epitaxial strain inhibits any population of the low-spin (S = 0) state with decreasing temperature. This observation identifies an important prerequisite for ferromagnetism in E-LCO thin films.