We report on the efficient spin-orbit torque (SOT) switching in a single ferromagnetic layer induced by a new type of inversion asymmetry, the composition gradient. The SOT of 6-to 60-nm epitaxial FePt thin films with a L1 0 phase is investigated. The magnetization of the FePt single layer can be reversibly switched by applying electrical current with a moderate current density. Different from previously reported SOTs which either decreases with or does not change with the film thickness, the SOT in FePt increases with the film thickness. We found the SOT in FePt can be attributed to the composition gradient along the film normal direction. A linear correlation between the SOT and the composition gradient is observed. This Rapid Communication introduces a platform to engineer large SOTs for lower-power spintronics.

Abstract2D transition metal dichalcogenides have attracted much attention in the field of spintronics due to their rich spin‐dependent properties. The promise of highly compact and low‐energy‐consumption spin‐orbit torque (SOT) devices motivates the search for structures and materials that can satisfy the requirements of giant perpendicular magnetic anisotropy (PMA) and large SOT simultaneously in SOT‐based magnetic memory. Here, it is demonstrated that PMA and SOT in a heavy metal/transition metal ferromagnet structure, Pt/[Co/Ni]2, can be greatly enhanced by introducing a molybdenum disulfide (MoS2) underlayer. According to first‐principles calculation and X‐ray absorption spectroscopy (XAS), the enhancement of the PMA is ascribed to the modification of the orbital hybridization at the interface of Pt/Co due to MoS2. The enhancement of SOT by the role played by MoS2 is explained, which is strongly supported by the identical behavior of SOT and PMA as a function of Pt thickness. This work provides new possibilities to integrate 2D materials into promising spintronics devices.

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Magnetic vortices are characterized by the senses of in-plane magnetization chirality and by the polarity of the vortex core. The electrical control of vortex polarity and chirality is highly demanded not only for fundamental understanding on spin dynamics in nano-disks under different circumstances, but also for technological applications, such as magnetic non-volatile memories and spin torque oscillators for neuromorphic computing. Here we report a novel approach that enables one to electrically control both the vortex chirality and polarity with low energy consumption. Thorough micromagnetic simulations, we show that in thin nano-disks of diameter larger than 160 nm, with the presence of current-induced Oersted field, the dynamic transformation of the edge solitons is able to efficiently switch both vortex chirality and polarity with low current under certain circumstances. We then developed an approach to directly write any of the four vortex states by electrical current pulses from a random state. We further investigated the switching phase diagram as a function of disk diameters. The results show that the switching process is highly size-dependent. As disk diameter is smaller than 160 nm, the switch of VC chirality and polarity always takes place at the same time, resulting in an unchanged handedness before and after switch. Furthermore, the critical switch current can be as low as 6 2 3 10 / cm A × , indicating a possible way for low current switch of vortex chirality in small disks.defines the handedness of the vortex with 1 CP = and 1 CP = − being catalyzed as left and right handed vortices, respectively. Being one of the most interesting magnetic soliton, vortex can be used as an information carrier and is currently attracting much more attention for a number of applications. Magnetic vortex have been proposed as memory bit in non-volatile storage for many years [3,4], for its multi-bit information storage and high stability [5,6]. Very recently, vortex was introduced as a building block for a robust sensor application in the automotive industry [7], where a large linear range is discovered. In addition, vortex-based spin torque nano-oscillators have been demonstrated being building blocks for neuromorphic computing, which is one of research topics towards low-power artificial intelligence application [ 8 , 9 ]. A full understanding on the electrical control of vortex dynamics and the switching process is a key towards those applications. In the past decades, great efforts have been made for searching effective methods to control the vortex polarity and chirality.The VC is very stable, and a static field of above 0.5 T field is required to switch its polarity, while to switch vortex chirality requires even more energy [5,6]. Fortunately, further studied showed that it can be efficiently switched through a dynamic process [10].When excited, the VC will be driven into gyrotropic precession, and polarity reversal happens when the VC reaches a certain critical velocity [ 11,12,13], through the formation and...

Exploring novel two-dimensional multiferroic materials that can realize electricfield control of two-dimensional magnetism has become an emerging topic in spintronics. Using first-principles calculations, we demonstrate that non-metallic bilayer transition metal dichalcogenides (TMDs) can be an ideal platform for building multiferroics by intercalated magnetic atoms. Moreover, we unveil that with Co intercalated bilayer MoS 2 , Co(MoS 2 ) 2 , two energetic degenerate states with opposite chirality of Dzyaloshinskii-Moriya interaction (DMI) are the ground states, indicating electric-field control of the chirality of topologic magnetism such as skyrmions can be realized in this type of materials by reversing the electric polarization. These findings pave the way for electric-field control of topological magnetism in two-dimensional multiferroics with intrinsic magnetoelectric coupling.