Strain-Induced Atomic-Scale Building Blocks for Ferromagnetism in Epitaxial LaCoO3
Sangmoon Yoon1, Xiang Gao1, Jong Mok Ok1
1Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
Nano Letters
|April 30, 2021
Summary
Strain in LaCoO3 thin films induces ferromagnetism not directly from strain, but from compressed structural units within twin-wall domains. These units exhibit high-spin/low-spin order, explaining the material's magnetic properties.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Magnetism
Background:
- Strain-induced ferromagnetism in LaCoO3 (LCO) thin films is robust but its origin remains unclear.
- Decade-long research efforts have not fully elucidated the mechanisms behind this phenomenon.
Purpose of the Study:
- To investigate the precise origin of strain-induced ferromagnetism in LaCoO3 thin films.
- To clarify the role of structural changes and magnetic ordering in ferromagnetic properties.
Main Methods:
- Combined scanning transmission electron microscopy (STEM) with ab initio density functional theory plus U (DFT+U) calculations.
- Analyzed structural units and magnetic ordering within ferroelastic twin-wall domains.
Main Results:
- Ferromagnetism arises from compressed structural units within ferroelastic twin-wall domains, not directly from strain.
- These compressed units display magnetically active rocksalt-type high-spin/low-spin order.
Conclusions:
- The ferroelastic nature of structural units is crucial for understanding ferromagnetism in LCO thin films.
- Strain's effect is mediated by the creation of specific, magnetically active structural configurations.
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