Reliability of spin-to-charge conversion measurements in graphene-based lateral spin valves

Abstract

Understanding spin physics in graphene is crucial for developing future two- dimensional spintronic devices. Recent studies show that efficient spin-to-charge conversions via either the inverse spin Hall effect or the inverse Rashba-Edelstein effect can be achieved in graphene by proximity with an adjacent spin-orbit coupling material. Lateral spin valve devices, made up of a graphene Hall bar and ferromagnets, are best suited for such studies. Here, we report that signals mimicking the inverse Rashba-Edelstein effect can be measured in pristine graphene possessing negligible spin-orbit coupling, confirming that these signals are unrelated to spin-to-charge conversion. We identify either the anomalous Hall effect in the ferromagnet or the ordinary Hall effect in graphene induced by stray fields as the possible sources of this artefact. By quantitatively comparing these options with finite-element-method simulations, we conclude the latter better explains our results. Our study deepens the understanding of spin-to-charge conversion measurement schemes in graphene, which should be taken into account when designing future experiments.

Omnidirectional spin-to-charge conversion in graphene/NbSe$_2$ van der Waals heterostructures

“…The overlap between both curves confirms that R avg follows sin(θ M ). However, the conventional Hall effect in the graphene channel induced by the stray fields from the ferromagnetic spin injector can also lead to similar signals [9,40]. To confirm that R avg is induced by SCC, we have measured R SCC in sample 2 as a function of an out-of-plane magnetic field to induce in-plane spin precession, an unequivocal proof for spin transport (see Supplementary Information section S9).…”

All-Electrical Spin-to-Charge Conversion in Sputtered BixSe1-x

“…Additionally, the stray field of CoFe-induced OHE is calculated by 3D FEM simulation based on the Hall coefficient of BiSe/NM structures obtained by applying the out-of-plane magnetic field to each structure. 31 We obtained less than a 0.3 mΩ OHE contribution for both structures. As shown in Figure Next, we analyzed the thickness dependence of the SCC signal by a 3D FEM simulation 7 also taking into account the AHE and the OHE discussed above (see Note S4 in the Supporting Information for details).…”

“…We should mention that an anomalous Hall effect (AHE) ,, and ordinary Hall effect (OHE) can appear as artifacts in the measured SCC signals (Note S3 in the Supporting Information). The anomalous Hall angle obtained by applying an out-of-plane magnetic field to CoFe in our own devices is 1.5%.…”

“…The contribution of the AHE was calculated by 3D finite element method (FEM) based on the spin diffusion model7,29,30,32 , and we obtained less than 6 mΩ and 2 mΩ AHE signals in the whole thickness range for BiSe/Ti and BiSe/Pt structures, respectively. Additionally, the stray field of CoFe-induced OHE is calculated by 3D FEM simulation based on the Hall coefficient of BiSe/NM structures obtained by applying the out-of-plane magnetic field to each structure31 . We obtained less than 0.3 mΩ OHE contribution for both structures.…”

Twist-Angle Controlled Collinear Edelstein Effect in van der Waals Heterostructures

“…The technique hinges upon the different behaviors of the x, ŷ, and ẑ polarization channels (and hence the SGE, CSGE, and ISHE nonlocal signals) under pseudo-time-reversal operations that invert certain components of an applied oblique field B = (B x , 0, B z ) in the Oxz plane, as we shall see briefly. First we note that in realistic devices the nonlocal voltage will include spurious contributions unrelated to spin transport (e.g., due to the ordinary Hall effect induced by stray fields [33,35,53]). To filter out nonspin-related effects, we consider the output nonlocal resistance difference between opposite initial configurations of the spin-injector: ∆R nl = (V nl,ny>0 −V nl,ny<0 )/2I, where n = n(B) is the spin-injector magnetization unit vector.…”