Abstract <p>In this work, we have investigated the effect of locally embedded in situ multilayer graphene (ML‑Gr) on the magnetic and spin-transport properties of Pt/Co/Pt thin-film structures with perpendicular magnetic anisotropy (PMA). It is found that the introduction of ML-Gr into the Co/Pt top interface leads to a significant increase in the spin–orbit torque (SOT) efficiency χ from 5.8 to 9.5 Oe/mA for Pt(5 nm)/Co(0.5 nm)/ Pt(7.5 nm) samples with a thicker top Pt layer upon incorporation of graphene. We attribute this improvement to an increase in the spin transparency of the Co/ML-Gr/Pt interface, which allows for more efficient use of the spin current generated by the bulk spin Hall effect (SHE) in the thick bottom platinum layer. Magneto-optical Kerr effect (MOKE) measurements demonstrate preservation of the coercive force and the rectangular shape of the hysteresis loop, ruling out significant changes in the PMA or domain structure. However, a sharp attenuation of the MOKE signal by a factor of 7.8 is observed. We attribute this attenuation to optical interference effects and absorption in the ML-Gr layer, rather than to changes in macroscopic magnetization. Our study highlights the dual role of graphene: as a spin transport optimizer and as an optical response modifier, which is critical for the development of highly efficient spin-orbitron devices.</p>