Evolution of Zero-Field Ferrimagnetic Domains and Skyrmions in Exchange-Coupled Pt/CoGd/Pt Confined Nanostructures: Implications for Antiferromagnetic Devices

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Magnetic skyrmions are small-sized spin textures with nontrivial topology that behave like charged particles under a spin-polarized current. The efficient use of skyrmions on the next generation of technological devices will depend on the controllable creation of sub-100 nm skyrmions, ideally without any external field. We report on the magnetic domains and skyrmions evolution in nanostructured ferrimagnetic Pt/CoGd/Pt multilayers discs at zero magnetic field and room temperature. The tuning of the magnetic structures is studied as a function of the disc size. The ferrimagnetic labyrinthine stripes are succeeded by the formation of multiple or single isolated ferrimagnetic skyrmions depending on the diameter of the disc. Multiple ferrimagnetic skyrmions present an average size of ∼120 nm, whereas single skyrmions ∼70 nm. It indicates a strong effect played by the confinement of the disc in modifying the skyrmions density and size. Our results shed light on the single ferrimagnetic skyrmion stability at zero magnetic field, which is a further drive in the realization of antiferromagnetic spintronic devices such as skyrmion-based spin torque nano-oscillators with implications in neuromorphic computing.