The electrical control of the non-trivial topology in Weyl antiferromagnets is of great interest for the development of next-generation spintronic devices. Recent studies suggest that the spin Hall effect can switch the topological antiferromagnetic order. However, the switching efficiency remains relatively low. Here, we demonstrate the effective manipulation of antiferromagnetic order in the Weyl semimetal Mn₃Sn using orbital torques originating from either metal Mn or oxide CuO_x. Although Mn₃Sn can convert orbital current to spin current on its own, we find that inserting a heavy metal layer, such as Pt, of appropriate thickness can effectively reduce the critical switching current density by one order of magnitude. In addition, we show that the memristor-like switching behaviour of Mn₃Sn can mimic the potentiation and depression processes of a synapse with high linearity—which may be beneficial for constructing accurate artificial neural networks. Our work paves a way for manipulating the topological antiferromagnetic order and may inspire more high-performance antiferromagnetic functional devices.

For real-world applications, it is desirable to realize field-free spin–orbit torque (SOT) switching in thin films with high perpendicular magnetic anisotropy (PMA). In this paper, we report that field-free SOT switching in a L1₀-FePt single layer with a large switching ratio of 26% is obtained by using a MgO ⟨100⟩⋀8°/⟨100⟩ miscut substrate. It is found that field-free switching depends on the direction of the imposed pulse current. Only when the electric current is along the y (010)-direction but not along the x (100)-direction does field-free switching happen, which can be attributed to the tilted PMA induced symmetry breaking in the x–z plane. Furthermore, under the field-free condition, our FePt single layer system exhibits stable multi-state magnetic switching behavior and nonlinear synaptic characteristics. This work paves the way to realize field-free SOT switching in the L1₀-FePt single layer, which will have significant impact on spin memory devices and synaptic electronics.

Spintronic could be used to simulate synapses or neurons due to its multistate storage characteristics. In this work, a reliable design of all-spin spiking neural networks (SNN) based on spin–orbit torque (SOT) devices has been proposed in A1 CoPt single layer. The CoPt-SOT devices exhibited field-free SOT switching, and the magnetization reversal mechanism was inferred to be a combination of domain nucleation and domain-wall propagation as observed through magneto-optical Kerr microscopy images. Moreover, the current-induced SOT switching process of the device exhibited stable multistate magnetic switching behavior, which can be controlled by varying the amplitude and pulse width of the current pulse. Meanwhile, the spike-timing-dependent plasticity (STDP) curve was inverted when the SOT switching polarity was reversed by different magnetic fields, and the change in anomalous Hall resistances (ΔRH) in the STDP curve was linearly related to the SOT switching ratio. In addition, at the zero magnetic field, we constructed an all-spin SNN using STDP synapses and leaky integrate-and-fire neurons of CoPt-SOT devices. The handwritten digits recognition rate of this all-spin SNN network was 89.9%. These results substantiate that the CoPt single layer represents a promising hardware solution for high-performance neuromorphic computing, with applicability in the domain of SNN.