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Precise Cu/ferromagnet interface resistance determination

Ascertain the precise interface resistance at the Cu/Py (Permalloy) and Cu/Ni interfaces in the lateral spin valve geometries used, in order to enable accurate experimental assignment of the perpendicular spin relaxation length and reliable extraction of spin Hall parameters.

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Background

Accurate determination of spin relaxation lengths, particularly the perpendicular component in ferromagnets, is sensitive to the assumed interface resistance at Cu/ferromagnet junctions. In the reported analysis, the authors note that assigning precise values is hindered by uncertainty in the interface resistance, which critically impacts quantitative extraction of both spin diffusion and spin Hall quantities. Resolving this parameter would reduce modeling ambiguity and improve the fidelity of anisotropy measurements.

References

Indeed we do observe a reduction of $\lambda_\mathrm{s}{\perp}$ compared to $\lambda_\mathrm{s}{\parallel}$ in both materials, although given the very small values involved for $\lambda_\mathrm{s}{\perp}$ it is difficult to assign an accurate value experimentally, particularly given the dependence on the interface resistance which cannot be precisely determined (Note S2 ).

— Measuring the magnetic anisotropy of the spin Hall effect and spin relaxation length in nickel and permalloy via electrical spin injection (2510.15809 - Dolan et al., 17 Oct 2025) in Section: Spin Absorption Anisotropy (main text)