Switchable orbital polarization and magnetization in strained LaCo O3 films

Er Jia Guo; Ryan D. Desautels; David Keavney; Andreas Herklotz; T. Zac Ward; Michael R. Fitzsimmons; Ho Nyung Lee

doi:10.1103/PhysRevMaterials.3.014407

Switchable orbital polarization and magnetization in strained LaCo O3 films

Er Jia Guo, Ryan D. Desautels, David Keavney, Andreas Herklotz, T. Zac Ward, Michael R. Fitzsimmons, Ho Nyung Lee

Materials Science and Technology Div

Research output: Contribution to journal › Article › peer-review

36 Scopus citations

Abstract

Strain engineering of epitaxial heterostructures offers opportunities to control the orbital degree of freedom by lifting the degeneracy of eg states. Here, we show that the orbital occupation in LaCoO3 (LCO) films can be switched between two degenerate eg bands with epitaxial strain. The orbital polarization of nearly -100% (or 100%) is controlled by depleting occupation of the dx2-y2(ord3z2-r2) orbital entirely in LCO for large compressive (or moderate tensile) strain. The change of electronic configuration associated with the spin-state transition modulates the magnetization of strained LCO films. Under compressive strain, LCO films exhibit a small magnetization without long-range ferromagnetic ordering. With tensile-strain increases, the magnetization of LCO films increases and reaches the maximum value when the bonding angle (Co-O-Co) is close to 180°C and the in-plane bond length (Co-O) is unstretched. Our results highlight the role of octahedral distortion and spin-state crossover in tailoring the magnetic properties of cobaltite thin films, suggesting an attractive route to deliberately control the orbital polarization that can be tuned to maximize the functionality of oxide heterostructures.

Original language	English
Article number	014407
Journal	Physical Review Materials
Volume	3
Issue number	1
DOIs	https://doi.org/10.1103/PhysRevMaterials.3.014407
State	Published - Jan 15 2019

Funding

We thank Yaohua Liu, Changhee Sohn, and Hyoungjeen Jeen for valuable discussions. This work was supported by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. T.Z.W. was supported through the DOE Early Career Research Program for a part of the magnetic data analysis. This research used resources of the Advanced Photon Source, a US DOE Office of Science User Facility operated by Argonne National Laboratory under Contract No. DE-AC02-06CH1135 (XAS). This work was partly supported by the Hundred Talent Program from Chinese Academy of Sciences during manuscript revision and further data analysis. This work was supported by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. T.Z.W. was supported through the DOE Early Career Research Program for a part of the magnetic data analysis. This research used resources of the Advanced Photon Source, a US DOE Office of Science User Facility operated by Argonne National Laboratory under Contract No. DE-AC02-06CH1135 (XAS). This work was partly supported by the Hundred Talent Program from Chinese Academy of Sciences during manuscript revision and further data analysis.

Funders	Funder number
DOE Office of Science
US Department of Energy
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Argonne National Laboratory	DE-AC02-06CH1135
Division of Materials Sciences and Engineering
Chinese Academy of Sciences

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abstract = "Strain engineering of epitaxial heterostructures offers opportunities to control the orbital degree of freedom by lifting the degeneracy of eg states. Here, we show that the orbital occupation in LaCoO3 (LCO) films can be switched between two degenerate eg bands with epitaxial strain. The orbital polarization of nearly -100% (or 100%) is controlled by depleting occupation of the dx2-y2(ord3z2-r2) orbital entirely in LCO for large compressive (or moderate tensile) strain. The change of electronic configuration associated with the spin-state transition modulates the magnetization of strained LCO films. Under compressive strain, LCO films exhibit a small magnetization without long-range ferromagnetic ordering. With tensile-strain increases, the magnetization of LCO films increases and reaches the maximum value when the bonding angle (Co-O-Co) is close to 180°C and the in-plane bond length (Co-O) is unstretched. Our results highlight the role of octahedral distortion and spin-state crossover in tailoring the magnetic properties of cobaltite thin films, suggesting an attractive route to deliberately control the orbital polarization that can be tuned to maximize the functionality of oxide heterostructures.",

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Switchable orbital polarization and magnetization in strained LaCo O3 films

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