High-accuracy MOKE detection of spin Hall–induced spin accumulation

Accumulation and conversion of spin and orbital momentum enclose great potential in spin/orbitronics, although direct quantifications are scarce. Magneto-Optic Kerr Effect (MOKE) has been used to get direct evidence of magnetic accumulation generated by a charge current density (J) in late transition metals (Pt) as well as in light transition elements (Ti, Cr). This effect is quantified by extracting the θ K /J ratio, where θ K represent the Kerr rotation angle. Significant discrepancies, exceeding one order of magnitude, are present for the reported θ K /J values, prompting revisions of methods and results. Here, we report on a novel methodology for MOKE measurements, providing high accuracy and, in this case, a sensitivity of (354 ± 27) nV/nrad. The designed protocol was tested in a 50 nm thick Pt, extracting a | \(\:{θ\:}KS\) /J| = 7.92 ± 1.94 nrad/(10 7 A/cm 2 ), which largely differs from earlier reported data for similar Pt films. As differences in Pt microstructure alone cannot account for such a discrepancy, our results highlight the need for standardized high-accuracy protocols enabling cross-laboratory comparisons in nanoradian polarimetry.