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