Giant Dampinglike-Torque Efficiency in Naturally Oxidized Polycrystalline TaAs Thin Films

Wilson Yanez; Yongxi Ou; Run Xiao; Supriya Ghosh; Jyotirmay Dwivedi; Emma Steinebronn; Anthony Richardella; K. Andre Mkhoyan; Nitin Samarth

doi:10.1103/PhysRevApplied.18.054004

Giant Dampinglike-Torque Efficiency in Naturally Oxidized Polycrystalline TaAs Thin Films

Wilson Yanez, Yongxi Ou, Run Xiao, Supriya Ghosh, Jyotirmay Dwivedi, Emma Steinebronn, Anthony Richardella, K. Andre Mkhoyan, Nitin Samarth

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

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Abstract

We report the measurement of efficient charge-to-spin conversion at room temperature in Weyl semimetal-ferromagnet heterostructures with both oxidized and pristine interfaces. Polycrystalline films of the Weyl semimetal, TaAs, are grown by molecular beam epitaxy on (001) GaAs and interfaced with a metallic ferromagnet (Ni0.8Fe0.2). Spin-torque ferromagnetic resonance (ST FMR) measurements yield a spin-torque ratio as large as ?FMR=0.45±0.25 in samples with an oxidized interface. By studying ST FMR in these samples with varying Ni0.8Fe0.2 layer thickness, we find that the dampinglike-torque efficiency is ?DL=1.36±0.66. In samples with a pristine (unoxidized) interface, the spin-torque ratio is ?FMR=-0.27±0.14 and has opposite sign to that observed in oxidized samples. We also find a lower bound on the spin Hall conductivity (424±110?/e S/cm), which is surprisingly consistent with theoretical predictions for the single-crystal Weyl semimetal state of TaAs.

Original language	English (US)
Article number	054004
Journal	Physical Review Applied
Volume	18
Issue number	5
DOIs	https://doi.org/10.1103/PhysRevApplied.18.054004
State	Published - Nov 2022

Bibliographical note

Funding Information:
The authors would like to thank D.C. Ralph for valuable comments and A. Sengupta for providing access to apparatus used in ST FMR measurements. The principal support for this project is provided by SMART, one of seven centers of nCORE, a Semiconductor Research Corporation program, sponsored by the National Institute of Standards and Technology (NIST). This supported the synthesis and standard characterization of heterostructures as well as charge-spin conversion measurements (W.Y., Y.O., J.D., N.S.) and their characterization using STEM (S.G., A.M.). Additional support for materials synthesis and characterization was provided by the Penn State Two-Dimensional Crystal Consortium-Materials Innovation Platform (2DCC-MIP) under NSF Grant No. DMR-2039351 (R.X., E.S., A.R., N.S.). Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC (Award No. DMR-2011401) and the NNCI (Award No. ECCS-2025124) programs.

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@article{527a2e8128734aa184e8dadc19cf55aa,

title = "Giant Dampinglike-Torque Efficiency in Naturally Oxidized Polycrystalline TaAs Thin Films",

abstract = "We report the measurement of efficient charge-to-spin conversion at room temperature in Weyl semimetal-ferromagnet heterostructures with both oxidized and pristine interfaces. Polycrystalline films of the Weyl semimetal, TaAs, are grown by molecular beam epitaxy on (001) GaAs and interfaced with a metallic ferromagnet (Ni0.8Fe0.2). Spin-torque ferromagnetic resonance (ST FMR) measurements yield a spin-torque ratio as large as ?FMR=0.45±0.25 in samples with an oxidized interface. By studying ST FMR in these samples with varying Ni0.8Fe0.2 layer thickness, we find that the dampinglike-torque efficiency is ?DL=1.36±0.66. In samples with a pristine (unoxidized) interface, the spin-torque ratio is ?FMR=-0.27±0.14 and has opposite sign to that observed in oxidized samples. We also find a lower bound on the spin Hall conductivity (424±110?/e S/cm), which is surprisingly consistent with theoretical predictions for the single-crystal Weyl semimetal state of TaAs.",

author = "Wilson Yanez and Yongxi Ou and Run Xiao and Supriya Ghosh and Jyotirmay Dwivedi and Emma Steinebronn and Anthony Richardella and Mkhoyan, {K. Andre} and Nitin Samarth",

note = "Funding Information: The authors would like to thank D.C. Ralph for valuable comments and A. Sengupta for providing access to apparatus used in ST FMR measurements. The principal support for this project is provided by SMART, one of seven centers of nCORE, a Semiconductor Research Corporation program, sponsored by the National Institute of Standards and Technology (NIST). This supported the synthesis and standard characterization of heterostructures as well as charge-spin conversion measurements (W.Y., Y.O., J.D., N.S.) and their characterization using STEM (S.G., A.M.). Additional support for materials synthesis and characterization was provided by the Penn State Two-Dimensional Crystal Consortium-Materials Innovation Platform (2DCC-MIP) under NSF Grant No. DMR-2039351 (R.X., E.S., A.R., N.S.). Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC (Award No. DMR-2011401) and the NNCI (Award No. ECCS-2025124) programs. Publisher Copyright: {\textcopyright} 2022 American Physical Society. ",

year = "2022",

month = nov,

doi = "10.1103/PhysRevApplied.18.054004",

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AU - Yanez, Wilson

AU - Ou, Yongxi

AU - Xiao, Run

AU - Ghosh, Supriya

AU - Dwivedi, Jyotirmay

AU - Steinebronn, Emma

AU - Richardella, Anthony

AU - Mkhoyan, K. Andre

AU - Samarth, Nitin

N1 - Funding Information: The authors would like to thank D.C. Ralph for valuable comments and A. Sengupta for providing access to apparatus used in ST FMR measurements. The principal support for this project is provided by SMART, one of seven centers of nCORE, a Semiconductor Research Corporation program, sponsored by the National Institute of Standards and Technology (NIST). This supported the synthesis and standard characterization of heterostructures as well as charge-spin conversion measurements (W.Y., Y.O., J.D., N.S.) and their characterization using STEM (S.G., A.M.). Additional support for materials synthesis and characterization was provided by the Penn State Two-Dimensional Crystal Consortium-Materials Innovation Platform (2DCC-MIP) under NSF Grant No. DMR-2039351 (R.X., E.S., A.R., N.S.). Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC (Award No. DMR-2011401) and the NNCI (Award No. ECCS-2025124) programs. Publisher Copyright: © 2022 American Physical Society.

PY - 2022/11

Y1 - 2022/11

N2 - We report the measurement of efficient charge-to-spin conversion at room temperature in Weyl semimetal-ferromagnet heterostructures with both oxidized and pristine interfaces. Polycrystalline films of the Weyl semimetal, TaAs, are grown by molecular beam epitaxy on (001) GaAs and interfaced with a metallic ferromagnet (Ni0.8Fe0.2). Spin-torque ferromagnetic resonance (ST FMR) measurements yield a spin-torque ratio as large as ?FMR=0.45±0.25 in samples with an oxidized interface. By studying ST FMR in these samples with varying Ni0.8Fe0.2 layer thickness, we find that the dampinglike-torque efficiency is ?DL=1.36±0.66. In samples with a pristine (unoxidized) interface, the spin-torque ratio is ?FMR=-0.27±0.14 and has opposite sign to that observed in oxidized samples. We also find a lower bound on the spin Hall conductivity (424±110?/e S/cm), which is surprisingly consistent with theoretical predictions for the single-crystal Weyl semimetal state of TaAs.

AB - We report the measurement of efficient charge-to-spin conversion at room temperature in Weyl semimetal-ferromagnet heterostructures with both oxidized and pristine interfaces. Polycrystalline films of the Weyl semimetal, TaAs, are grown by molecular beam epitaxy on (001) GaAs and interfaced with a metallic ferromagnet (Ni0.8Fe0.2). Spin-torque ferromagnetic resonance (ST FMR) measurements yield a spin-torque ratio as large as ?FMR=0.45±0.25 in samples with an oxidized interface. By studying ST FMR in these samples with varying Ni0.8Fe0.2 layer thickness, we find that the dampinglike-torque efficiency is ?DL=1.36±0.66. In samples with a pristine (unoxidized) interface, the spin-torque ratio is ?FMR=-0.27±0.14 and has opposite sign to that observed in oxidized samples. We also find a lower bound on the spin Hall conductivity (424±110?/e S/cm), which is surprisingly consistent with theoretical predictions for the single-crystal Weyl semimetal state of TaAs.

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Giant Dampinglike-Torque Efficiency in Naturally Oxidized Polycrystalline TaAs Thin Films

Abstract

Bibliographical note

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University of Minnesota Materials Research Science and Engineering Center (DMR-2011401)

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Giant Dampinglike-Torque Efficiency in Naturally Oxidized Polycrystalline TaAs Thin Films

Abstract

Bibliographical note

MRSEC Support

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University of Minnesota Materials Research Science and Engineering Center (DMR-2011401)

IRG-1: Ionic Control of Materials

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