Spin-orbit torque magnetic random-access memory (SOT-MRAM) is attracting considerable interests for which offers sub-nanosecond writing speed, femtojoule-level energy consumption, and virtually unlimited endurance. However, large-scale industrial implementation is constrained by the lack of proper spin-source materials that simultaneously exhibit a large spin-orbit torque efficiency, low resistivity, and compatibility with the established SOT-MRAM fabrication process. Stimulated by recent progress of the complementary generation of orbital and spin currents, we engineer $\beta \text{−}\mathrm{W}/X$ ($X=\text{Ti}$, V, Cr, Ru, Ta) multilayers to resolve these constraints. Harmonic Hall and current switching measurements demonstrate that substantially enhanced spin-orbit torque efficiencies and reduced critical switching current densities can be achieved in W/Ti, W/V, W/Cr, and W/Ta multilayers, as compared with that of the pure $\beta \text{−}\mathrm{W}$. Upon further optimizing the thicknesses of Cr and W layers, we realize a low critical switching current density down to $5\times {10}^5\mathrm{A}/{\mathrm{cm}}^2$, which represents nearly an order of magnitude lower than that of pure $\beta \text{−}\mathrm{W}$. The scaling relation between the spin-orbit torque efficiency and resistivity can be qualitatively captured by a charge-orbital-spin conversion mechanism. These results provide practical guidelines for designing energy-efficient spin-source materials that could accelerate the application of SOT-MRAM technologies.

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• Electrical generation of spin carriers
• Magnetization switching
• Spin current
• Spin-orbit torque
• Spintronics