Enhancement of perpendicular magnetic anisotropy in Co/Ni multilayers by in situ annealing the Ta/Cu under-layers

The perpendicular magnetic properties of glass/Ta/Cu/[Co/Ni]₄/Ta multilayers can be efficiently tuned by in situ pre-annealing the Ta/Cu under-layers at various temperatures (T_Cu) before the deposition of the Co/Ni stack. As a result of the co-effect of fcc(111) texture and Cu surface roughness, the perpendicular anisotropy K_u and coercivity H _c⊥ exhibit a similar non-monotonous dependence on the T _Cu, showing minimum values at T_Cu = 100 °C and maxima at 400 °C for K_u while at 550 °C for H_c⊥. By in situ annealing the under-layers at 550 °C and then post-annealing the whole stack at 250 °C, the H_c⊥ value can be significantly enhanced from 139 Oe up to 620 Oe, which is important for spintronic applications.