Construction of a Room-Temperature Pt/Co/Ta Multilayer Film with Ultrahigh-Density Skyrmions for Memory Application

Magnetic skyrmions are chiral quasiparticles that show promise for storage of information. At present, the achievable skyrmion density (η_Sk) is generally low (10-20 μm^-2) because of the lack of effective manipulation. Here, both the magnetic anisotropy ( K_eff) and interfacial Dzyaloshinskii-Moriya interaction (DMI) of [Pt/Co/Ta] _n multilayer films are elaborately modulated by changing the Co thickness ( t_Co) to study the η_Sk dependence of intrinsic properties of the films systematically. The experimental and simulated results confirm that both the DMI and K_eff have significant modifications on η_Sk, and their respective contributions vary with t_Co. Only when the magnetic anisotropy transits from out-of-plane to in-plane at an appropriate t_Co range (1.8-2.1 nm) does the K_eff decrease and the DMI increase with the t_Co. Both the factors are favorable to the skyrmion formation and increase the density synergistically, toggling a maximal η_Sk value of 45 μm^-2. These findings provide a criterion for designing the high η_Sk magnetic film, which may advance the development of high-density skyrmion-based magnetic memorizers.