Engineered materials for all-optical helicity-dependent magnetic switching

Journal name:
Nature Materials
Volume:
13,
Pages:
286–292
Year published:
DOI:
doi:10.1038/nmat3864
Received
Accepted
Published online

Abstract

The possibility of manipulating magnetic systems without applied magnetic fields have attracted growing attention over the past fifteen years. The low-power manipulation of the magnetization, preferably at ultrashort timescales, has become a fundamental challenge with implications for future magnetic information memory and storage technologies. Here we explore the optical manipulation of the magnetization in engineered magnetic materials. We demonstrate that all-optical helicity-dependent switching (AO-HDS) can be observed not only in selected rare earth–transition metal (RE–TM) alloy films but also in a much broader variety of materials, including RE–TM alloys, multilayers and heterostructures. We further show that RE-free CoIr-based synthetic ferrimagnetic heterostructures designed to mimic the magnetic properties of RE–TM alloys also exhibit AO-HDS. These results challenge present theories of AO-HDS and provide a pathway to engineering materials for future applications based on all-optical control of magnetic order.

At a glance

Figures

  1. Schematic of the four types of ferromagnetic sample that have been studied and exhibit AO-HDS.
    Figure 1: Schematic of the four types of ferromagnetic sample that have been studied and exhibit AO-HDS.

    a, Thin-film RE–TM alloys. b, [RE/TM]N multilayers. c, Exchange-coupled [RE/TM]N/[RE/TM]M heterostructures. d, SFI made of two TM layers antiferromagnetically coupled through 0.4 nm Ir interlayers. Each type of magnetic structure has shown either AO-HDS or thermal demagnetization depending on the thickness, layer structure and/or atomic concentration of the sample.

  2. Examples of the two optical responses for two different samples.
    Figure 2: Examples of the two optical responses for two different samples.

    a,b, [Co(0.8 nm)/Tb(0.4 nm)]×21 multilayers showing thermal demagnetization (TD, a) and [Co(0.5 nm)/Tb(0.4 nm)]×28 multilayers showing AO-HDS (b). For each sample, three types of polarized laser beam were swept over the sample and the magnetization pattern was subsequently imaged: from top to bottom, right circularly polarized light (σ+), left circularly polarized light (σ) and linearly polarized light (L). In the images, dark contrast corresponds to one orientation of magnetization and light contrast the opposite.

  3. Response to optical excitation for RE–TM alloys (GdxFeCo1−x, TbxCo1−x, DyxCo1−x, HoxFeCo1−x) and two types of RE–TM multilayer ([Tb/Co] and [Ho/CoFe]) as a function of the RE concentration (x).
    Figure 3: Response to optical excitation for RE–TM alloys (GdxFeCo1−x, TbxCo1−x, DyxCo1−x, HoxFeCo1−x) and two types of RE–TM multilayer ([Tb/Co] and [Ho/CoFe]) as a function of the RE concentration (x).

    Red dots indicate thermal demagnetization and green stars AO-HDS. All of these alloys show perpendicular anisotropy except the two GdFeCo alloys marked IP (for in-plane anisotropy). The shaded regions correspond to alloy compositions for which TMcomp is below room temperature. For the multilayers the RE layer thicknesses varied from 0.3 to 0.5 nm and the TM layers varied from 0.25 to 1.0 nm.

  4. Samples swept with circularly polarized beams (σ+ or σ− ).
    Figure 4: Samples swept with circularly polarized beams (σ+ or σ ).

    All-optical switching can be observed for three different samples: a Tb26Co74 alloy, a [Tb(0.3 nm)/Co(0.3 nm)]×42 multilayer and a [Tb(2.5 nm)/Co(2.5 nm)]×5 multilayer, which have the same average concentration of Tb and Co atoms.

  5. Magnetic measurements of a Ta(4 nm)/Pd(3 nm)/[Co(1 nm)/Ir/Co(0.4 nm)/Ni(0.6 nm)/Pt(0.3 nm)/Co(0.4 nm)/Ir]5/Pd(3 nm) SFI structure.
    Figure 5: Magnetic measurements of a Ta(4 nm)/Pd(3 nm)/[Co(1 nm)/Ir/Co(0.4 nm)/Ni(0.6 nm)/Pt(0.3 nm)/Co(0.4 nm)/Ir]5/Pd(3 nm) SFI structure.

    a, Remanent magnetization M and coercive field HC as a function of temperature allow us to define a compensation temperature at TMcomp=380 K. b, Images after scanning the laser with three types of polarized beam that were swept over the sample: from top to bottom, right circularly polarized light (σ+), left circularly polarized light (σ) and linearly polarized light (L).

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Affiliations

  1. Center for Magnetic Recording Research, University of California San Diego La Jolla, California 92093-0401 USA

    • S. Mangin,
    • M. Gottwald,
    • C-H. Lambert,
    • V. Uhlíř &
    • E. E. Fullerton
  2. Institut Jean Lamour, UMR CNRS 7198 – Université de Lorraine – boulevard des aiguillettes BP 70239, Vandoeuvre cedex F-54506 France

    • S. Mangin,
    • C-H. Lambert,
    • M. Hehn &
    • G. Malinowski
  3. Department of Physics and Research Center OPTIMAS University of Kaiserslautern Erwin Schroedinger Str. 46 Kaiserslautern D-67663 Germany

    • D. Steil,
    • S. Alebrand,
    • M. Cinchetti &
    • M. Aeschlimann
  4. Department of Electrical and Computer Engineering, University of California San Diego La Jolla, California 92093-0401 USA

    • L. Pang,
    • Y. Fainman &
    • E. E. Fullerton
  5. Laboratoire de Physique des Solides, Université Paris-Sud, CNRS UMR 8502 Orsay 91405 France

    • G. Malinowski

Contributions

S.M., M.H., Y.F., M.A. and E.E.F. designed and coordinated the project; M.G., C-H.L., M.H., G.M. and S.M. grew, characterized and optimized the samples. C-H.L., D.S., L.P., S.A., V.U., M.C. and S.M. built and operated the Kerr microscope and the pump laser set-up. S.M. and E.E.F. coordinated work on the paper with contributions from D.S., M.H., S.A., M.C., M.A. and regular discussions with all authors.

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