Neuromorphic computing (NC) is gaining wide acceptance as a potential technology to achieve lowpower intelligent devices. To realize NC, researchers investigate various types of synthetic neurons and synaptic devices, such as memristors and spintronic devices. In comparison, spintronics-based neurons and synapses have potentially higher endurance. However, for realizing low-power devices, domain wall (DW) devices that show DW motion at low energies�typically below pJ/bit�are favored. Here, we demonstrate DW motion at current densities as low as 10 6 A/m 2 by engineering the β-W spin−orbit coupling (SOC) material. With our design, we achieve ultralow pinning fields and current density reduction by a factor of 10 4 . The energy required to move the DW by a distance of about 18.6 μm is 0.4 fJ, which translates into the energy consumption of 27 aJ/bit for a bit-length of 1 μm. With a meander DW device configuration, we have established a controlled DW motion for synapse applications and have shown the direction to make ultralow energy spin-based neuromorphic elements.

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Neuromorphic computing (NC) has been gaining attention as a potential candidate for artificial intelligence. The building blocks for NC are neurons and synapses. Research studies have indicated that domain wall (DW) devices are one of the most energy-efficient contenders for realizing NC. Moreover, synaptic functions can be achieved by obtaining multi-resistance states in DW devices. However, in DW devices with no artificial pinning, it is difficult to control the DW position, and hence achieving multilevel resistance is difficult. Here, we have proposed the concept of nanoscale interfacial Dzyaloshinskii-Moriya interaction (iDMI) for controllably stopping the DWs at specific positions, and hence, realizing multi-resistance states. We show that the nanoscale iDMI forms an energy barrier (well), which can controllably pin the DWs at the pinning sites. Moreover, a tunable depinning current density was achieved by changing the width and iDMI constant of the confinement region. We have also studied pinning in a device with five successive pinning sites. This feature is a proof-of-concept for realizing multi-resistance states in the proposed concept. Based on these observations, a magnetic tunnel junction-where the free layer is made up of the proposed concept-can be fabricated to achieve synapses for NC applications.