Effect of Ta insertion between Pt and CoFeB on interfacial magnetic anisotropy in Pt/CoFeB/MgO multilayer thin-film stack

The effect of a thin Ta layer inserted between Pt and CoFeB layers on perpendicular magnetic anisotropy (PMA) with MgO barrier layer has been studied. The crystallinity was studied by performing high-resolution x-ray diffraction (HR-XRD) technique. While the crystal peak of Pt is observed in all sample stack that is oriented as (111) face-centered cubic crystal structure, a very weak and broad α-Ta (110) peak is observed when Ta layer thickness is above 0.8 nm. Magneto-optical Kerr effect (MOKE) measurements show that the PMA could be enhanced by inserting Ta layer between Pt and CoFeB layer. The magnetically dead layer thickness (t_dead) and the interfacial anisotropy energy density (K_i) of the various Ta-inserted layer thickness were found as 0.135 nm; 0.75 erg/cm², 0.141 nm; 1.02 erg/cm², 0.187 nm; 1.15 erg/cm², for t_Ta = 0.0, 0.5, and 1.0 nm, respectively. Both t_dead and K_i increase with Ta-inserted layer thickness in Pt/Ta(t)/CoFeB/MgO multilayer film stack. The sources of interfacial magnetic anisotropy can be hybridization, crystallinity properties, and/or B/Ta diffusion effect at the interfaces in Pt/Ta(t)/CoFeB/MgO multilayer film stack.