Tailoring Magnetic Skyrmion Dimensions via Precise Interface Roughness Modulation in W‐Inserted Skyrmion SOT Channel Grown on <i>β</i> ‐Phase W Seed Layer

Abstract For skyrmion‐based perpendicular (p) Spin‐Orbit‐Torque (SOT) magnetic random‐access‐memory (MRAM), a tungsten (W)‐inserted skyrmion SOT channel was designed by a precise modulation of the W insert layer thickness ( t w,insert ) having 0.100–0.142 nm as well as the interface roughness ( R a,interf,sky ) having 18.13–33.73 pixel density (a.u.) between ferromagnet Co 2 Fe 6 B 2 free layer and MgO tunneling barrier. An inverse relation was found between R a,interf,sky and t w,insert ; i.e., a higher R a,interf,sky required a smaller t w,insert . In addition, R a,interf,sky is critically determined by the surface roughness ( R a,surf,seed ) of the β ‐phase SOT seed layer having 0.120–0.138 nm. A higher R a,surf,seed induced significantly a higher R a,interf,sky . Particularly, a precise design of the skyrmion diameter (0.96–0.62 µm) and density (0.093–0.140 ea/µm 2 ) found that a higher R a,interf,sky led to a smaller skyrmion diameter and a higher skyrmion density. These results demonstrate a practical possibility of a skyrmion‐based SOT MRAM via a new inserted material and its related precise modulation of R a,interf,sky .