Programmable magnetic field-free manipulation of perpendicular magnetization switching is essential for the development of ultralow-power spintronic devices. However, the magnetization in a centrosymmetric single-layer ferromagnetic film cannot be switched directly by passing an electrical current in itself. Here, we demonstrate a repeatable bulk spin-orbit torque (SOT) switching of the perpendicularly magnetized CoPt alloy single-layer films by introducing a composition gradient in the thickness direction to break the inversion symmetry. Experimental results reveal that the bulk SOT-induced effective field on the domain walls leads to the domain walls motion and magnetization switching. Moreover, magnetic field-free perpendicular magnetization switching caused by SOT and its switching polarity (clockwise or counterclockwise) can be reversibly controlled in the IrMn/Co/Ru/CoPt heterojunctions based on the exchange bias and interlayer exchange coupling. This unique composition gradient approach accompanied with electrically controllable SOT magnetization switching provides a promising strategy to access energy-efficient control of memory and logic devices.

The carrier mobility of the as-mentioned building block devices depends mainly on the device fabrication technology and the channel semiconductors. The fabrication technology is complex and each of the processes is crucial to the carrier mobility of the as-fabricated building block devices. For example, Park et al. pointed out that the peak electron mobility of graphene field-effect-transistors (FETs) can be improved up to four times by using a cleaner substrate during the device fabrication process. [4] On the other hand, the carrier mobility of the as-mentioned building block devices can be regulated by the crystallinity, growth plane, carrier effective mass, carrier concentration, etc. of channel semiconductors. With a better crystallinity, InGaZnO nanowires (NWs)-, [5] β-Ga 2 O 3 nanosheets-, [6] and black phosphorus filmbased FETs [7] have shown the enhanced mobilities in the kinds of literature, owing to the decreased transport scattering. Meanwhile, with a designed crystal growth plane, the polarity, carrier effective mass, and surface scattering of InP NWs, [8] layered PtSe 2 , [9] and multilayer InSe [10] can be controlled, resulting in the higher mobilities of FETs.

A simple, reliable, and self-switchable spin−orbit torque (SOT)-induced magnetization switching in a ferromagnetic single layer is needed for the development of next generation fully electrical controllable spintronic devices. In this work, fieldfree SOT-induced magnetization switching in a CoPt single layer is realized by broken multiple inversion symmetry through simultaneously introducing both oblique sputtering and a vertical composition gradient. A quantitative analysis indicates that multiple inversion asymmetries can produce dynamical bias fields along both z-and x-axes, leading to the observed field-free deterministic magnetization switching. Our study provides a method to accomplish fully electrical manipulation of magnetization in a ferromagnetic single layer without the external magnetic field and auxiliary heavy metal layer, enabling flexible design for future spin−orbit torque-based memory and logic devices.

Controllable spin–orbit torque based nonvolatile memory is highly desired for constructing energy efficient reconfigurable logic-in-memory computing suitable for emerging data-intensive applications. Here, we report our exploration of the IrMn/Co/Ru/CoPt/CoO heterojunction as a potential candidate for applications in both multistate memory and programmable spin logic. The studied heterojunction can be programmed into four different magnetic configurations at will by tuning both the in-plane exchange bias at the interface of IrMn and Co layers and the out-of-plane exchange bias at the interface of CoPt and CoO layers. Moreover, on the basis of the controllable exchange bias effect, 10 states of nonvolatile memory and multiple logic-in-memory functions have been demonstrated. Our findings indicate that IrMn/Co/Ru/CoPt/CoO multilayered structures can be used as a building block for next-generation logic-in-memory and multifunctional multidimensional spintronic devices.

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