Optimality of linear vacancy defect for skyrmion nucleation

Magnetic skyrmions offer a pathway to ultra-dense, low-power memory, but writing them efficiently remains a challenge. Using atomistic spin simulations and minimum energy path calculations in a PdFe/Ir(111) film, we show that deliberately placing linear chains of four atomic vacancies cuts the skyrmion nucleation barrier nearly in half-down to 44.7 meV at 3.75 T-compared to 85 meV in a pristine track. Linear defects excel because they remove high-energy core regions during skyrmion creation while minimally disturbing its outer negative energy halo during depinning. This geometry-driven effect relies only on generic energy density profiles, making it broadly applicable to all skyrmion-hosting materials.