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All-electric switching of perpendicular magnetization is a prerequisite for the integration of fast, high-density, and low-power magnetic memories and magnetic logic devices into electric circuits. To date, the field-free spin-orbit torque (SOT) switching of perpendicular magnetization has been observed in SOT bilayer and trilayer systems through various asymmetric designs, which mainly aim to break the mirror symmetry. Here, we report that the perpendicular magnetization of CoxPt100-x single layers within a special composition range (20 < x < 56) can be deterministically switched by electrical current in the absence of external magnetic field. Specifically, the Co30Pt70 shows the largest out-of-plane effective field efficiency and best switching performance. We demonstrate that this unique property arises from the cooperation of two structural mechanisms: the low crystal symmetry property at the Co platelet/Pt interfaces and the composition gradient along the thickness direction. Compared with that in bilayers or trilayers, the field-free switching in CoxPt100-x single layer greatly simplifies the SOT structure and avoids additional asymmetric designs.

Neuromorphic computing has become an increasingly popular approach for artificial intelligence because it can perform cognitive tasks more efficiently than conventional computers. However, it remains challenging to develop dedicated hardware for artificial neural networks. Here, a simple bilayer spintronic device for hardware implementation of neuromorphic computing is demonstrated. In L11‐CuPt/CoPt bilayer, current‐inducted field‐free magnetization switching by symmetry‐dependent spin–orbit torques shows a unique domain nucleation‐dominated magnetization reversal, which is not accessible in conventional bilayers. Gradual domain nucleation creates multiple intermediate magnetization states which form the basis of a sigmoidal neuron. Using the L11‐CuPt/CoPt bilayer as a sigmoidal neuron, the training of a deep learning network to recognize written digits, with a high recognition rate (87.5%) comparable to simulation (87.8%) is further demonstrated. This work offers a new scheme of implementing artificial neural networks by magnetic domain nucleation.

Spin–orbit torque provides a highly efficient way to achieve current-induced magnetization switching, which relies on charge-to-spin conversion of the spin source layer. However, in the conventional heavy metal/ferromagnetic layer, the generated spin–orbit torque is limited to in-plane, which cannot deterministically switch the perpendicularly magnetized ferromagnets, and thus impedes practical application for high-density magnetic memory. In this work, deterministic switching of perpendicular magnetization is achieved in the SrRuO3/WTe2 bilayer structure, which is attributed to the out-of-plane spin polarization originated from the van der Waals material WTe2. The out-of-plane spin polarization is further confirmed by the shift of the anomalous Hall effect loop. Spin polarization matrix analysis indicates that the reduced crystal symmetry in WTe2 is responsible for the out-of-plane spin polarization.

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