Tailoring Gilbert damping of ferromagnetic metals via heterostructure and alloy engineering

The Landau-Lifshitz-Gilbert (LLG) equation is the fundamental equation describing the temporal evolution of the magnetization vector of ferromagnets, which simultaneously incorporates the precessional motion around the effective field and the damping relaxation toward the equilibrium state for the magnetization vector. Gilbert damping, the phenomenological parameter governing energy dissipation in the LLG equation, is central to the performance of modern spintronic devices. Its manipulation through materials engineering has become a vibrant field of research, driven by the need for both ultra-low damping for energy-efficient operation and enhanced damping for fast magnetization switching. This topical review provides an overview of recent advances in tailoring Gilbert damping of ferromagnetic metals, focusing on two powerful strategies: heterostructure engineering and alloy engineering. In heterostructures, we first review how the ferromagnetic layer thickness determines the Gilbert damping. We then discuss how the choice, thickness and electronic structure of adjacent nonmagnetic layers, including heavy metals, topological insulators, ferroelectrics and doped semiconductors, enable attractive damping phenomena. In alloy engineering, we survey low‑doping and high‑doping regimes, highlighting ultra‑low damping values below 10^-3in systems. Finally, we offer study perspectives on emerging directions of Gilbert damping, including the search for materials with intrinsic density‑of‑states valleys near the Fermi level, further exploration and research on anisotropic damping, and twist engineering in van der Waals heterostructures as a new degree of freedom for damping control. This review aims to provide understanding of the microscopic origins of Gilbert damping and to guide the rational design of low‑loss, high‑speed spintronic devices.