Field-Free Spin-Orbit-Torque Switching in Co/Pt/Co Multilayer with Mixed Magnetic Anisotropies

Spin-orbit-torque- (SOT) induced magnetization switching in a Co/Pt/Co trilayer, with two Co layers exhibiting magnetization easy axes orthogonal to each other is investigated. A Pt layer is used as a source of spin-polarized current as it is characterized by relatively high spin-orbit coupling. The spin Hall angle of Pt, theta = 0.08, is quantitatively determined using the spin-orbit-torque ferromagnetic resonance technique. In addition, Pt serves as a spacer between two Co layers and depending on its thickness, different interlayer-exchange-coupling (IEC) energy between ferromagnets is induced. Intermediate IEC energies, resulting in a top Co magnetization tilted from the perpendicular direction, allows for SOT-induced field-free switching of the top Co layer. The switching process is discussed in more detail, showing the potential of the system for neuromorphic applications.