Capping layer dependent anti-correlation between magnetic damping and spin-orbital to charge conversion

Abstract: The magnetic Gilbert damping and spin-orbital to charge interconversion phenomenon play vital role in controlling the modern spintronics device performances. Though the ferromagnets (FMs) and heavy metals (HMs) are considered to be the key components of the future spin-orbit torque magnetic random access memory (SOT-MRAM) devices, recently the integration of lighter materials with low intrinsic spin-orbit coupling (SOC) in spintronics devices has proven to be noteworthy. Here we demonstrate the efficient control of magnetization dynamics of $\beta$-W/CoFeB bilayer when capped by low SOC organic and inorganic layers. The C${60}$ capping layer (CL) significantly enhances the magnetization relaxation process compared to the CuO$_x$ in $\beta$-W/CoFeB/CL heterostructures, while the static magnetic properties remain in-different irrespective of the nature of CL. Interestingly, the spin-orbital to charge conversion phenomenon is found to be enhanced for $\beta$-W/CoFeB/CuO$_x$ stacking compared to the $\beta$-W/CoFeB/C${60}$ heterostructure, signifying the anti-correlation between the magnetic damping and spin-orbital to charge conversion. The results are interpreted by the interfacial phenomena, like the orbital Rashba effect, two-magnon scattering, and interfacial spin memory loss. Our detailed experimental investigations shed light on the importance of low SOC materials in effectively tuning the magnetization dynamics for the development of future power efficient spintronics devices.