Defect inducing large spin orbital coupling enhances magnetic recovery dynamics in CrI3 monolayer

The rapid magnetic recovery process (MRP) after photoexcitation is crucial for efficient information recording in magnets but is often impeded by insufficient spin flip channels. Using time-domain ab initio nonadiabatic molecular dynamics including spin-orbital coupling (SOC), we investigate MRP in a CrI3 ferromagnetic monolayer and find that defects can accelerate this process. In defect-free CrI3, MRP is slow (400 fs) due to weak SOC between spin-majority and spin-minority valence band edges, notably limiting spin flips during relaxation. Intrinsic vacancy defects (VI and VCr), particularly the VCr defect, disrupt the system’s rotational symmetry by extending their states asymmetrically to bulk I ions. The lowered symmetry significantly enhances SOC near the valence band edges and speeds up MRP to 100 fs by promoting spin flips. This study uncovers the origins of slow MRP in CrI3 monolayer and highlights defect engineering as a promising strategy to improve MRP for optically excited spintronic devices.