Spin–orbit torque (SOT) induced perpendicular magnetization switching in Pt1‐xGdx/Co/Al2O3 heterostructure with x = 0, 0.02, 0.14, 0.30, and 0.33 is investigated. With in‐plane charge current flowing through the Pt1‐xGdx layer, field‐free current‐induced magnetization switching is observed for all nonzero x due to the existence of opposite spin Hall angles (θSHA) from Pt1‐xGdx alloys. Furthermore, the large θSHA of about 0.27 is obtained in the optimal Pt0.70Gd0.30 alloy films, which is about four times larger than that of the pure Pt. This work suggests a simple and scalable method for realizing field‐free SOT switching, and provides potential candidates of spin Hall materials that can be used to produce highly efficient SOTs.

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Spin‐orbit torque (SOT)‐based magnetization switching is a promising candidate for the innovation and developments of spintronic devices. However, the necessity of an in‐plane magnetic field to induce deterministic switching is an obstacle to feasibility in practical applications. Here, it is shown that the field‐free current‐induced magnetization switching in a perpendicular magnetized Pt1−xMox/Co/Ru heterostructure with x = 0, 0.04, 0.07, 0.12, and 0.17. Applying an in‐plane charge current through the Pt1−xMox layer, the device can achieve a high‐efficiency field‐free current‐induced magnetization switching with competing spin currents generated from a single Pt1−xMox alloy layer due to opposite spin Hall angles (θSHA) of Pt and Mo atoms and locally induced electric field. Remarkably, the large θSHA of about 0.35 is achieved in the optimal composition of Pt0.88Mo0.12 alloy, which is much higher than that of the pure Pt structure. The results pave the way to resolve the future problems of scalability and thermal stability for SOT‐driven magnetic tunnelling junctions.