All-optical detection of the spin Hall angle in W/CoFeB/SiO2 heterostructures with varying thickness of the tungsten layer

Sucheta Mondal, Samiran Choudhury, Neha Jha, Arnab Ganguly, Jaivardhan Sinha, Anjan Barman

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    47 Scopus citations

    Abstract

    The development of advanced spintronics devices hinges on the efficient generation and utilization of pure spin current. In materials with large spin-orbit coupling, the spin Hall effect may convert charge current to pure spin current, and a large conversion efficiency, which is quantified by spin Hall angle (SHA), is desirable for the realization of miniaturized and energy-efficient spintronic devices. Here, we report a giant SHA in beta-tungsten (β-W) thin films in Sub/W(t)/Co20Fe60B20(3nm)/SiO2(2nm) heterostructures with variable W thickness. We employed an all-optical time-resolved magneto-optical Kerr effect microscope for an unambiguous determination of SHA using the principle of modulation of Gilbert damping of the adjacent ferromagnetic layer by the spin-orbit torque from the W layer. A nonmonotonic variation of SHA with W layer thickness (t) is observed with a maximum of about 0.4 at about t=3nm, followed by a sudden reduction to a very low value at t=6nm. This variation of SHA with W thickness correlates well with the thickness-dependent structural phase transition and resistivity variation of W above the spin-diffusion length of W, while below this length the interfacial electronic effect at W/CoFeB influences the estimation of SHA.

    Original languageBritish English
    Article number054414
    JournalPhysical Review B
    Volume96
    Issue number5
    DOIs
    StatePublished - 10 Aug 2017

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