AUTHOR=Wang Linxia , Liu Jieyu , Wu Minghui , Wu Hanming , Li Kaixiang , Shao Yuankai , Li Zhenguo , Wang Weichao 

TITLE=Strain-Induced Modulation of Spin Configuration in LaCoO3

JOURNAL=Frontiers in Materials

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2020.00060

DOI=10.3389/fmats.2020.00060

ISSN=2296-8016

ABSTRACT=<p>For oxides with octahedron ligand field, such as perovskite, spinel, and mullite, unit occupancy of <italic>e</italic><sub>g</sub> orbital plays a key role in governing the catalytic performance of oxygen redox in the application of renewable energy storage and conversion. The magnetic configurations greatly influence the <italic>e</italic><sub>g</sub> occupancy of these oxides. In this work, using the perovskite LaCoO<sub>3</sub> as an example, we use density functional theory (DFT) calculations to achieve an intermediate spin configuration corresponding to unit-like <italic>e</italic><sub>g</sub> occupancy via strain schemes. We determined that the introduction of strain by changing lattice constants effectively tailors electronic configurations. The low-spin (<inline-formula><mml:math id="INEQ1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi>t</mml:mi><mml:mrow><mml:mn>2</mml:mn><mml:mo>⁢</mml:mo><mml:mi mathvariant="normal">g</mml:mi></mml:mrow><mml:mn>6</mml:mn></mml:msubsup><mml:mo>⁢</mml:mo><mml:msubsup><mml:mi>e</mml:mi><mml:mrow><mml:mtext>g</mml:mtext></mml:mrow><mml:mn>0</mml:mn></mml:msubsup></mml:mrow></mml:math></inline-formula>), intermediate-spin (<inline-formula><mml:math id="INEQ2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi>t</mml:mi><mml:mrow><mml:mn>2</mml:mn><mml:mo>⁢</mml:mo><mml:mi mathvariant="normal">g</mml:mi></mml:mrow><mml:mn>5</mml:mn></mml:msubsup><mml:mo>⁢</mml:mo><mml:msubsup><mml:mi>e</mml:mi><mml:mrow><mml:mtext>g</mml:mtext></mml:mrow><mml:mn>1</mml:mn></mml:msubsup></mml:mrow></mml:math></inline-formula>), and high-spin (<inline-formula><mml:math id="INEQ3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi>t</mml:mi><mml:mrow><mml:mn>2</mml:mn><mml:mo>⁢</mml:mo><mml:mi mathvariant="normal">g</mml:mi></mml:mrow><mml:mn>4</mml:mn></mml:msubsup><mml:mo>⁢</mml:mo><mml:msubsup><mml:mi>e</mml:mi><mml:mrow><mml:mtext>g</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msubsup></mml:mrow></mml:math></inline-formula>) configurations are obtained with the strain γ &lt; 1.0%, 1.0% ≤ γ &lt; 4.0%, and γ ≥ 4.0%, respectively. To obtain the <italic>e</italic><sub>g</sub> unit occupancy practically, Ba with a larger ionic radius relative to La is inserted into A site to replace La elements, introducing tensile strain to the pristine LaCoO<sub>3</sub>. The Ba substitution of La leads to the desirable spin configuration with the unit-like <italic>e</italic><sub>g</sub> occupancy. These findings provide a scenario on how to precisely control the unit occupancy of <italic>e</italic><sub>g</sub> via defect induced strain.</p>