Controllable intrinsic Gilbert damping in Pt buffered [Co/Ni]n multilayers with enhanced perpendicular magnetic anisotropy

We systematically investigate the magnetization precession processes of post-prepared and after-annealing Pt buffered [Co/Ni]n multilayers with adjustable perpendicular magnetic anisotropy (PMA) by time-resolved magneto-optical Kerr effect. The PMA of the [Co/Ni]n multilayers could be modulated by changing the number of Co/Ni periods n, Pt thickness tPt and annealing temperature Ta, respectively. With a fixed tPt, both uniaxial magnetic anisotropy Ku and intrinsic damping constant alpha 0 could be modulated by the variation of n. We observed that alpha 0 is linearly proportional to Ku, since both of them originate from the spin-orbit coupling (SOC). For a fixed n, with the increase of tPt, Ku exhibits a non-monotonic change behavior, but alpha 0 increases monotonously. It is found that alpha 0 shows a nonlinear positve correlation to Ku. It suggests that the SOC is not the only factor affecting the damping process. Finally, for the specific sample, both alpha 0 and Ku also display the different variation behaviors with increasing Ta. In this case, the changes in film microstructure caused by the annealing have different contributions to Ku and alpha 0, resulting in a negative correlation between Ku and alpha 0. The findings could be helpful to design the potential application of [Co/Ni]n multilayers system in STT-MRAM with high density, low power and high thermal stability.

Automated summary

This study systematically investigates the magnetization precession processes of post-prepared and after-annealing Pt buffered [Co/Ni]n multilayers with adjustable perpendicular magnetic anisotropy (PMA) using time-resolved magneto-optical Kerr effect. The findings reveal a linear proportionality between the intrinsic damping constant alpha 0 and the uniaxial magnetic anisotropy Ku, as well as non-monotonic behavior in Ku with increasing Pt thickness tPt. Additionally, it is observed that alpha 0 shows a nonlinear positive correlation with Ku, suggesting that spin-orbit coupling is not the only factor affecting the damping process.