Field-Free Spin-Orbit Torque Switching in Perpendicularly Magnetized Synthetic Antiferromagnets

Synthetic antiferromagnets (SAFs), formed through an interlayer antiferromagnetic exchange coupling of ferromagnetic layers, exhibit intriguing potential in next-generation spintronic devices due to the zero net magnetization and the high thermal stability. Compared to ferromagnets that are conventionally widely employed, SAFs are expected to significantly improve the data density and stability due to the suppression of the net stray field. Thus far, it has been well established that the spin-orbit torque (SOT) switching of SAF requires an in-plane effective magnetic field to break inversion symmetry and thereby assist the Landau-Lifshitz dynamics. This field can either be externally applied or achieved through the exchange coupling given by an adjacent ferromagnetic layer. Such requirement hinders the application of SAFs since a net magnetization cannot be ruled out. Here, the field-free SOT switching of an all-SAF system with a significantly reduced net magnetization is demonstrated. The switching is demonstrated to be robust up to approximate to 460 K. This work paves the way for the practical applications of the SAFs in the SOT-based memory devices.