Temperature Dependence of Magnetic Properties in CoFe/Tb Multilayers with Perpendicular Magnetic Anisotropy

Rare earth/transition metal multilayers with tunable net magnetization (M_net) and perpendicular magnetic anisotropy (PMA) are potential systems for achieving devices with high speed and density. In this paper, we perform a detailed study on the temperature (T) and thickness dependences of perpendicular magnetic properties in [Co₈₀Fe₂₀(0.45 nm)/Tb (x = 0.3-0.95 nm)]₅multilayers. The strong antiferromagnetic (AF) interaction between Tb and CoFe spins is demonstrated at the interfaces, and the magnetization compensation thickness (at which M_nettends to zero) is determined as x ∼0.6 nm at room temperature. Whether the multilayer is Tb-rich or CoFe-rich, an increasing trend in magnetic coercivity is found with the decrease in T, demonstrating that the M_netof the AF-coupled region is always dominated by CoFe in this structure. Furthermore, the transient polar MOKE signals were also measured at elevated T by using laser pulse heating. With the increase in pump fluence, the original rectangle loop changes to a two-step switching shape for the sample with 0.4 nm Tb due to the decreased PMA strength and increased interfacial atomic diffusion. However, for the multilayer with 0.9 nm Tb that is farther from compensation, the loop becomes very inclined since the PMA is relatively weak and nearly vanishes upon laser impulsion. These results provide a deep insight into the key roles of sublayer thicknesses and interfaces, which are very helpful for achieving efficient control of the spintronic devices based on the AF-coupled materials.