Extended Data Figure 4.

Spin-Magnetoresistances for a geometry with platinum wires along the x axis (spin-accumulation μ_y along y). a, For a magnetic field H along x (grey dots). The jump in resistance at 6 T corresponds to the spin-flop field. b, For a magnetic field H along y (black dots). (The solid lines correspond to regression fit of the H-along-y data of the spin mixing conductances from Extended Data Eqs. 3, 4 and 5, yielding $g_n^{(\uparrow \downarrow )}$ = 12.76 /nm² and $g_{im}^{(\uparrow \downarrow )}$ = 74.82 /nm². The two field directions are fitted together with $g_{im}^{(\uparrow \downarrow )}$ = 0, and K/J = 0.025 and D/J = 0.011, using λ = 2 nm, θ_SH = 0.1 and ρ₀= 40 μΩ.cm for the normal metal wires)