Magnetic skyrmions are attracting interest as efficient information‐storage devices with low energy consumption, and have been experimentally and theoretically investigated in multilayers including ferromagnets, ferrimagnets, and antiferromagnets. The 3D spin texture of skyrmions demonstrated in ferromagnetic multilayers provides a powerful pathway for understanding the stabilization of ferromagnetic skyrmions. However, the manipulation mechanism of skyrmions in antiferromagnets is still lacking. A Hall balance with a ferromagnet/insulating spacer/ferromagnet structure is considered to be a promising candidate to study skyrmions in synthetic antiferromagnets. Here, high‐density Néel‐type skyrmions are experimentally observed at zero field and room temperature by Lorentz transmission electron microscopy in a Hall balance (core structure [Co/Pt]n/NiO/[Co/Pt]n) with interfacial canted magnetizations because of interlayer ferromagnetic/antiferromagnetic coupling between top and bottom [Co/Pt]n multilayers, where the Co layers in [Co/Pt]n are always ferromagnetically coupled. Micromagnetic simulations show that the generation and density of skyrmions are strongly dependent on interlayer exchange coupling (IEC) and easy‐axis orientation. Direct experimental evidence of skyrmions in synthetic antiferromagnets is provided, suggesting that the proposed approach offers a promising alternative mechanism for room‐temperature spintronics.

Perpendicular magnetization switching driven by spin‐orbit torque (SOT) exhibits nonvolatility and adjustability, which has great potential applications in magnetic random‐access memory and neuromorphic computing. In this work, the SOT efficiency in the Pt (001)/NiFe (Py) and Pt (111)/Py bilayers is first investigated, where the single crystal Pt films and polycrystalline Py films are grown by molecular beam epitaxy and magnetron sputtering, respectively. The (001)‐oriented Pt sample shows a larger SOT efficiency than that of the (111)‐oriented one, which is mainly attributed to the facet‐dependent intrinsic spin Hall effect of the Pt layer related to the Berry curvature of the electrical band structure. Then, the epitaxial Pt (001)‐based perpendicularly magnetized multilayers are designed to study the perpendicular magnetization switching driven by SOT. A continuous and stable reversal is successfully achieved, providing a conceivable candidate for reliable and variable imitation of the artificial synapses. The magneto–optical Kerr effect imaging proves that the sustainable change of magnetization state originates from the multiple site domain nucleation and growth in the ferromagnetic layer. This work provides an efficient method to enhance the SOT efficiency, as well as employs the epitaxial thin films in artificial synaptic devices for neuromorphic computing.

Electrical switching of magnetization through spin-orbit torque (SOT) induced by a composition gradient in single-layer L1 0 -FePt has garnered considerable research interest owing to its inherent superior perpendicular magnetic anisotropy (PMA) that provides ultrahigh capacity to magnetic storage and memory devices. However, a large in-plane external magnetic field is typically required to assist SOT-driven switching, which is still a limitation for the practical application of L1 0 -FePt. This study reports realizable field-free magnetization switching by SOT via Cr doping to form a singlelayer magnetic structure with an in-plane magnetization component oriented toward L1 0 -FeCrPt [110] direction that strongly depends on the magnetocrystalline anisotropy. The Cr doping yields a considerable in-plane exchangecoupling effective field that is conducive toward disintegrating the rotational switching symmetry and facilitates field-free switching in single-layer films with PMA. Furthermore, this in-plane effective field exhibits a nonmonotonic evolution with respect to the Cr-doping concentration, which is validated using first-principles calculation with a frustration-based model of magnetic exchange interactions. Thus, this study delivers an attractive method to facilitate the field-free electrical manipulations of magnetization in singlelayer ferromagnets to motivate innovative designs for advanced spintronics devices.

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