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 perpendicular to exhibit a similar non-monotonous dependence on the T-Cu, showing minimum values at T-Cu = 100 degrees C and maxima at 400 degrees C for K-u while at 550 degrees C for H-c perpendicular to. By in situ annealing the under-layers at 550 degrees C and then post-annealing the whole stack at 250 degrees C, the H-c perpendicular to value can be significantly enhanced from 139 Oe up to 620 Oe, which is important for spintronic applications. (C) 2013 AIP Publishing LLC.