The evolution of chemical ordering and property in Fe_1+xSe₂ upon intercalation ratios

Intercalation has been considered as an effective method to explore innovative two-dimensional (2D) materials and modify their properties. However, the relationship between intercalation concentration, structure, and property remains a largely uncharted territory, and the controllable synthesis of desired intercalated phases faces challenges. Here, a general intercalated rule for the effect of self-intercalation ratio on atomic arrangements is revealed. Then, the controllable synthesis of a series of Fe-intercalated 2D materials is realized. Scanning transmission electron microscopy illustrates that their intercalation structures undergo disordered/ordered/half-ordered/ordered transformation, which confirms the intercalated rule and proposes a new structure termed half-ordered intercalation. Notably, their magnetic and electrical properties can be significantly modulated by intercalation. Orderly intercalated nanoflakes possess room-temperature magnetism with composition-regulated magnetic domains. Moreover, Fe_1.5Se₂ and Fe_1.6Se₂ are scarce half-metallic materials showing different magneto-resistance behaviors. This work would guide the design and synthesis of new intercalated materials, and deepen the understanding of the relationship between structure and properties.