Extended Data Fig. 1: X-ray characterization of the nickel thin-film structure.

a, X-ray reflectivity data and fit of the sample using a four-layer model with the scattering length density profile shown in the inset. The dashed lines in the inset indicate the slab model of the corresponding layers. The best fit parameters obtained by fitting the XRR intensities are shown in the table. The errors are estimated by a 5% increase over the optimum logarithmic figure of merit. b, Out-of-plane XRD scan in the angular regime of 40° ≤ 2θ ≤60°. The observed intensities at 2θ ≈ 50.53° and 2θ ≈ 52.13° correspond to Cu(002) and Ni(002). The lack of any Cu(111) and Ni(111) intensities shows the epitaxial growth. The inset graph shows the rocking-scans over the Cu(002) and Ni(002) peak positions. c, In-plane XRD scan at an inclination angle Δχ = 54.51°. The intensities at 2θ ≈ 43.41° and 2θ ≈ 44.47° correspond to the Cu(111) and Ni(111) reflections, respectively. d, ϕ scans for the Ni(111), Cu(111) and Si(111) ip peaks, obtained at an inclination angle of Δχ = 54.74°. A clear fourfold symmetry of the Cu(111) and Ni(111) ip reflections is observed with an offset angle of 45° to the Si(111) substrate reflections. For reasons of clarity, the scans are shifted in intensity by a factor of two each. e, ϕ scans for the Cu(111) and Ni(111) reflections, obtained at inclination angles of Δχ = 15.80°, Δχ = 54.74° and Δχ = 79.00°. For clarity, the scans are shifted in intensity by 0.1 each. Cu(111) intensities are shown in the angular regime of 0° ≤ ϕ ≤180°, while the Ni(111) intensities are shown for 180° ≤ ϕ ≤360°.