Temperature-Dependent Magnetization Dynamics in Nanoscale Cu(t_Cu)/[Co/Ni]_N Perpendicular Multilayers: Implications for Spintronic Applications

Magnetic multilayers with perpendicular magnetic anisotropy (PMA) have significant advantages in the development of spintronic applications. However, currently, the research on the temperature (T) dependence of magnetization dynamics is mainly focused on the in-plane magnetized ferromagnetic materials. In this work, the magnetic properties of the effective PMA field Hkeff and intrinsic magnetic damping factor α0 were investigated at various T for the nanoscale Cu(tCu)/[Co/Ni]N perpendicular multilayers by the time-resolved magneto-optical Kerr effect approach. It is quite remarkable that both the Hkeff and α0 exhibit a peak value at T ∼ 180 K for thin films of N = 2 and 5. The nonmonotonic variation of Hkeff is resulting from the competition between the increased PMA constant Ku and saturation magnetization at low T, while the variation of α0 is caused by the coeffect of increased Ku and reduced two-magnon scattering that mainly arises from spin fluctuations in the magnetic dead layer (MDL) at the Cu/Co interface. In contrast, for the sample of N = 8 with a thick enough magnetic layer, Ku plays a dominant role in the observed variation behaviors within our measurement temperature range, resulting in a monotonically increased Hkeff and α0 with the decrease in T. Our results reveal that the magnetization dynamics are highly sensitive to the interfacial MDL at low T, which is of significance for the applications of practical spintronic devices with ultrafast control of information operation.