Ferroelectric Self-Polarization Controlled Magnetic Stratification and Magnetic Coupling in Ultrathin La0.67Sr0.33MnO3Films

Chao Liu; Yaohua Liu; Bangmin Zhang; Cheng Jun Sun; Da Lan; Pingfan Chen; Xiaohan Wu; Ping Yang; Xiaojiang Yu; Timothy Charlton; Michael R. Fitzsimmons; Jun Ding; Jingsheng Chen; Gan Moog Chow

doi:10.1021/acsami.1c02300

Ferroelectric Self-Polarization Controlled Magnetic Stratification and Magnetic Coupling in Ultrathin La_0.67Sr_0.33MnO₃Films

Chao Liu, Yaohua Liu, Bangmin Zhang, Cheng Jun Sun, Da Lan, Pingfan Chen, Xiaohan Wu, Ping Yang, Xiaojiang Yu, Timothy Charlton, Michael R. Fitzsimmons, Jun Ding, Jingsheng Chen, Gan Moog Chow

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

10 Scopus citations

Abstract

Multiferroic oxide heterostructures consisting of ferromagnetic and ferroelectric components hold the promise for nonvolatile magnetic control via ferroelectric polarization, advantageous for the low-dissipation spintronics. Modern understanding of the magnetoelectric coupling in these systems involves structural, orbital, and magnetic reconstructions at interfaces. Previous works have long proposed polarization-dependent interfacial magnetic structures; however, direct evidence is still missing, which requires advanced characterization tools with near-atomic-scale spatial resolutions. Here, extensive polarized neutron reflectometry (PNR) studies have determined the magnetic depth profiles of PbZr0.2Ti0.8O3/La0.67Sr0.33MnO3 (PZT/LSMO) bilayers with opposite self-polarizations. When the LSMO is 2-3 nm thick, the bilayers show two magnetic transitions on cooling. However, temperature-dependent magnetization is different below the lower-temperature transition for opposite polarizations. PNR finds that the LSMO splits into two magnetic sublayers, but the inter-sublayer magnetic couplings are of opposite signs for the two polarizations. Near-edge X-ray absorption spectroscopy further shows contrasts in both the Mn valences and the Mn-O bond anisotropy between the two polarizations. This work completes the puzzle for the magnetoelectric coupling model at the PZT/LSMO interface, showing a synergic interplay among multiple degrees of freedom toward emergent functionalities at complex oxide interfaces.

Original language	English
Pages (from-to)	30137-30145
Number of pages	9
Journal	ACS Applied Materials and Interfaces
Volume	13
Issue number	25
DOIs	https://doi.org/10.1021/acsami.1c02300
State	Published - Jun 30 2021

Funding

This work was supported by the Singapore Ministry of Education Academic Research Fund Tier 2 under the project no. MOE2018-T2-1-019 and Academic Research Fund AcRF Tier 1 grant under no. R-284-000-196-114. The authors would like to acknowledge the Singapore Synchrotron Light Source (SSLS) for accessing the facility necessary for conducting the research. The laboratory is a National Research Infrastructure under the National Research Foundation Singapore. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan [REF: http://energy.gov/downloads/doe-public-access-plan ]. We acknowledge Dr. Jong Keum for the X-ray reflectivity measurement. C.L. would like to acknowledge the Oak Ridge National Laboratory for the assignment of Short-Term Scholar as a visiting student. This research used resources of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, and was supported by the U.S. DOE under contract no. DE-AC02-06CH11357 and the Canadian Light Source and its funding partners.

Funders	Funder number
U.S. Department of Energy	DE-AC02-06CH11357
Office of Science
Argonne National Laboratory
Ministry of Education - Singapore	R-284-000-196-114, MOE2018-T2-1-019

Keywords

flexoelectric effect
interlayer coupling
magnetoelectric coupling
polarization reversal
two magnetic transitions

Access to Document

10.1021/acsami.1c02300

Cite this

Liu, C., Liu, Y., Zhang, B., Sun, C. J., Lan, D., Chen, P., Wu, X., Yang, P., Yu, X., Charlton, T., Fitzsimmons, M. R., Ding, J., Chen, J., & Chow, G. M. (2021). Ferroelectric Self-Polarization Controlled Magnetic Stratification and Magnetic Coupling in Ultrathin La_0.67Sr_0.33MnO₃Films. ACS Applied Materials and Interfaces, 13(25), 30137-30145. https://doi.org/10.1021/acsami.1c02300

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title = "Ferroelectric Self-Polarization Controlled Magnetic Stratification and Magnetic Coupling in Ultrathin La0.67Sr0.33MnO3Films",

abstract = "Multiferroic oxide heterostructures consisting of ferromagnetic and ferroelectric components hold the promise for nonvolatile magnetic control via ferroelectric polarization, advantageous for the low-dissipation spintronics. Modern understanding of the magnetoelectric coupling in these systems involves structural, orbital, and magnetic reconstructions at interfaces. Previous works have long proposed polarization-dependent interfacial magnetic structures; however, direct evidence is still missing, which requires advanced characterization tools with near-atomic-scale spatial resolutions. Here, extensive polarized neutron reflectometry (PNR) studies have determined the magnetic depth profiles of PbZr0.2Ti0.8O3/La0.67Sr0.33MnO3 (PZT/LSMO) bilayers with opposite self-polarizations. When the LSMO is 2-3 nm thick, the bilayers show two magnetic transitions on cooling. However, temperature-dependent magnetization is different below the lower-temperature transition for opposite polarizations. PNR finds that the LSMO splits into two magnetic sublayers, but the inter-sublayer magnetic couplings are of opposite signs for the two polarizations. Near-edge X-ray absorption spectroscopy further shows contrasts in both the Mn valences and the Mn-O bond anisotropy between the two polarizations. This work completes the puzzle for the magnetoelectric coupling model at the PZT/LSMO interface, showing a synergic interplay among multiple degrees of freedom toward emergent functionalities at complex oxide interfaces.",

keywords = "flexoelectric effect, interlayer coupling, magnetoelectric coupling, polarization reversal, two magnetic transitions",

author = "Chao Liu and Yaohua Liu and Bangmin Zhang and Sun, {Cheng Jun} and Da Lan and Pingfan Chen and Xiaohan Wu and Ping Yang and Xiaojiang Yu and Timothy Charlton and Fitzsimmons, {Michael R.} and Jun Ding and Jingsheng Chen and Chow, {Gan Moog}",

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Liu, C, Liu, Y, Zhang, B, Sun, CJ, Lan, D, Chen, P, Wu, X, Yang, P, Yu, X, Charlton, T, Fitzsimmons, MR, Ding, J, Chen, J & Chow, GM 2021, 'Ferroelectric Self-Polarization Controlled Magnetic Stratification and Magnetic Coupling in Ultrathin La_0.67Sr_0.33MnO₃Films', ACS Applied Materials and Interfaces, vol. 13, no. 25, pp. 30137-30145. https://doi.org/10.1021/acsami.1c02300

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AU - Liu, Chao

AU - Liu, Yaohua

AU - Zhang, Bangmin

AU - Sun, Cheng Jun

AU - Lan, Da

AU - Chen, Pingfan

AU - Wu, Xiaohan

AU - Yang, Ping

AU - Yu, Xiaojiang

AU - Charlton, Timothy

AU - Fitzsimmons, Michael R.

AU - Ding, Jun

AU - Chen, Jingsheng

AU - Chow, Gan Moog

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AB - Multiferroic oxide heterostructures consisting of ferromagnetic and ferroelectric components hold the promise for nonvolatile magnetic control via ferroelectric polarization, advantageous for the low-dissipation spintronics. Modern understanding of the magnetoelectric coupling in these systems involves structural, orbital, and magnetic reconstructions at interfaces. Previous works have long proposed polarization-dependent interfacial magnetic structures; however, direct evidence is still missing, which requires advanced characterization tools with near-atomic-scale spatial resolutions. Here, extensive polarized neutron reflectometry (PNR) studies have determined the magnetic depth profiles of PbZr0.2Ti0.8O3/La0.67Sr0.33MnO3 (PZT/LSMO) bilayers with opposite self-polarizations. When the LSMO is 2-3 nm thick, the bilayers show two magnetic transitions on cooling. However, temperature-dependent magnetization is different below the lower-temperature transition for opposite polarizations. PNR finds that the LSMO splits into two magnetic sublayers, but the inter-sublayer magnetic couplings are of opposite signs for the two polarizations. Near-edge X-ray absorption spectroscopy further shows contrasts in both the Mn valences and the Mn-O bond anisotropy between the two polarizations. This work completes the puzzle for the magnetoelectric coupling model at the PZT/LSMO interface, showing a synergic interplay among multiple degrees of freedom toward emergent functionalities at complex oxide interfaces.

KW - flexoelectric effect

KW - interlayer coupling

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KW - polarization reversal

KW - two magnetic transitions

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