Spin State Disproportionation in Insulating Ferromagnetic LaCoO3 Epitaxial Thin Films
Shanquan Chen1, Jhong-Yi Chang2, Qinghua Zhang3
1School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, 518055, China.
Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
|July 24, 2023
Summary
Strain-induced ferromagnetism in LaCoO3 films is explained by mixed spin states of cobalt ions. Tensile strain leads to a 1:3 ratio of high-spin to low-spin states, revealing spin state disproportionation and enabling new material properties.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Thin Film Magnetism
Background:
- The origin of insulating ferromagnetism in epitaxial LaCoO3 films under tensile strain is not well understood.
- The spin state of cobalt (Co) ions, crucial for ferromagnetism, remains undetermined in these films.
Purpose of the Study:
- To systematically investigate the spin state of Co ions in epitaxial LaCoO3 thin films.
- To clarify the mechanism of strain-induced ferromagnetism by determining the spin state.
Main Methods:
- Element-specific X-ray absorption spectroscopy and dichroism were employed.
- Configuration interaction cluster calculations were used for analysis.
Main Results:
- Co3+ ions in LaCoO3 films under compressive strain exhibit a low-spin state.
- Co3+ ions in LaCoO3 films under tensile strain show a mixed high-spin and low-spin state ratio of approximately 1:3.
- Observed dark strips in microscopy correspond to the high-spin Co3+ state, indicating spin state disproportionation.
Conclusions:
- The study elucidates the mechanism of strain-induced ferromagnetism in LaCoO3 films.
- Spin state degrees of freedom and strain engineering are key to creating novel properties in thin films.
- This work highlights the importance of spin state manipulation for advanced material design.
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