In spin-orbit torque (SOT) devices, a current is used to generate a spin current via a material with strong spin-orbit coupling, which then applies torque to an adjacent ferromagnetic layer, triggering magnetization switching.

The magnitude of the SOT determines the efficiency and reliability of magnetization switching, so achieving control and enhancement of the SOT is crucial for the operating speed, power consumption, and logic architecture design of the device.

SOT modulation based on multi-physical field coupling mechanisms has yet to be achieved due to limited modulation range and high driving voltages. At the same time, existing modulation methods are largely incompatible with current silicon-based integrated circuit (IC) processes, further restricting the performance, power consumption, practical application, and integrated development of tunable SOT devices.

Addressing the above scientific problems, the team of Professor Liu Ming from the National Key Laboratory of Precision Micro-Nano Manufacturing Technology, School of Electronic Science and Engineering, Xi'an Jiaotong University (XJTU), along with other collaborators, achieved small-voltage, high-efficiency spin control of NiFe/PtOx structure SOT devices based on silicon-based lead zirconate titanate [Pb(Zr, Ti)O3, PZT] thin films.

By designing the device structure to apply voltage on a silicon-based piezoelectric film, the NiFe/PtOx SOT is modulated in situ, and the modulation effect has good stability and recoverability. The NiFe/PtOx SOT was enhanced by up to 450 percent at a small voltage of 30 V.

The piezoelectric film-based device design can generate a higher electric field strength under a small voltage compared to bulk materials while satisfying silicon-based integration, thereby achieving an effective balance between "small voltage" and "high tuning".

First-principles calculations show that the electric field-induced stress and ion migration can significantly change the Berry curvature at the Fermi level of PtOx, thereby improving the spin-to-charge conversion efficiency and enhancing the SOT.

Combined with the effective modulation of magnetic anisotropy by electrostrictive stress, the prototype device can significantly improve the magnetization switching speed and power consumption performance.

The research results, titled A Widely Tunable Spin-Orbit Torque Device Through the Silicon Compatible CMOS Platform, were published in the internationally renowned journal Advanced Materials.