Influence of buffer layers on the texture and magnetic properties of Co/Pt multilayers with perpendicular anisotropy

A study on the buffer layer dependence of film texture, surface roughness, and magnetization reversal mechanism in Co/Pt multilayers is presented. Four different buffers are used: (A) 10 nm Cu, (B) 5 nm Ta/10 nm Cu, (C) 5 nm Ta/10 nm Cu/5 nm Ta, and (D) 5 nm Ta/10 nm Cu/5 nm Ta/10 nm Cu. The growth of [2 nm Pt/0.5 nm Co]5/2 nm Pt on top of these buffer layers results in a large variation of film textures and surface morphologies. Samples with a Cu buffer (A) exhibit a low degree of film texture and are relatively rough. MOKE and MFM measurements on these films reveal that the magnetization reverses by the nucleation of numerous small domains due to a large dispersion of the activation energy barrier. Buffer layer structures where the first layer consists of Ta, on the other hand, result in (111)-textured Co/Pt multilayers with a more regular surface morphology. In these samples, magnetization reversal proceeds by fast domain wall movement.