Enhancement of spin Hall angle by an order of magnitude via Cu intercalation in MoS ₂ /Co-Fe-B heterostructures

Transition-metal dichalcogenides (TMDs) are a novel class of quantum materials with significant potential in spintronics, optoelectronics, valleytronics, and optovalleytronics. TMDs exhibit strong spin-orbit coupling, enabling efficient spin-charge interconversion, which makes them ideal candidates for spin-orbit torque-driven spintronic devices. In this study, we have investigated the spin-to-charge conversion through ferromagnetic resonance in $\mathrm{Mo}\mathrm{S}$${}_{2}$/$\mathrm{Cu}$/$\mathrm{Co}$-$\mathrm{Fe}$-$\mathrm{B}$ heterostructures with varying $\mathrm{Cu}$ spacer thicknesses. The conversion efficiency, quantified by the spin Hall angle, has been enhanced by an order of magnitude due to $\mathrm{Cu}$ intercalation. Magneto-optic Kerr effect microscopy has confirmed that $\mathrm{Cu}$ does not significantly modify the magnetic domains, indicating its effectiveness in decoupling $\mathrm{Mo}\mathrm{S}$${}_{2}$ from $\mathrm{Co}$-$\mathrm{Fe}$-$\mathrm{B}$. This decoupling preserves the spin-orbit coupling (SOC) of $\mathrm{Mo}\mathrm{S}$${}_{2}$ by mitigating the exchange interaction with $\mathrm{Co}$-$\mathrm{Fe}$-$\mathrm{B}$, as proximity to localized magnetization can alter the electronic structure and the SOC. First-principles calculations have revealed that $\mathrm{Cu}$ intercalation notably enhances the spin Berry curvature and spin Hall conductivity, contributing to the increased spin Hall angle. This study demonstrates that interface engineering of ferromagnet--TMD-based heterostructures can achieve higher spin-to-charge conversion efficiencies, paving the way for advancements in spintronic applications.