Giant Spin-Orbit Torque in Antiferromagnetic-Coupled Pt/[Co/Gd] Multilayers with Suppressed Spin Dephasing and Robust Thermal Stability.

Manipulating magnetization via power-efficient spin-orbit torque (SOT) has garnered significant attention in the field of spin-based memory and logic devices. However, the damping-like SOT efficiency (ξ) in heavy metal (HM)/ferromagnetic metal (FM) bilayers is relatively small due to the strong spin dephasing accompanied by additional spin polarization decay. Furthermore, the perpendicular magnetic anisotropy (PMA) originating from the HM/FM interface is constrained by the thickness of FM, which is unfavorable for thermal stability in practical applications. Consequently, it is valuable to develop systems that not only exhibit large ξ but also balance thermal stability. In this work, we designed antiferromagnetic-coupled [Co/Gd] multilayers, where staggered Co and Gd magnetic moments effectively suppress the spin dephasing and additional spin polarization decay. The ordered Co-Gd arrangements along the out-of-plane direction provide bulk PMA, endowing Pt/[Co/Gd] high thermal stability. The SOT of Pt/[Co/Gd] was systematically studied with N, demonstrating a significantly large ξ of up to 0.66. The ξ of Pt/[Co/Gd] is greater than those of Pt/Co and Pt/ferrimagnetic alloys. This significant enhancement relies on the effective suppression of spin dephasing in [Co/Gd]. Our work highlights that the antiferromagnetic-coupled [Co/Gd] multilayer is a promising candidate for low-consumption and high-density spintronic devices.