Robust High-Spin State in One-Dimensional CrX2 (X = Cl, Br, I) at the Single-Chain Limit

Low-dimensional magnetic materials have garnered significant interest due to their unique physical properties and potential applications. Nevertheless, the synthesis of one-dimensional (1D) magnetic materials presents challenges, and the properties of these 1D materials at the single-chain limit have not been well investigated. We here explore experimentally and theoretically 1D CrX2 (X= Cl, Br, I) magnetic single chains residing within carbon nanotubes. Single chains of CrX2 are confirmed by the atomic-resolution scanning transmission electron microscopy (STEM) imaging and spectroscopy analysis. Electron energy loss spectroscopy clearly reveals the high-spin state of the Cr atoms within the chain. Notably, we present the first precise measurement and analysis of Cr spin state at the single-chain level, revealing that these spin states can be controlled by the local atomic bonding configuration (CrX2 versus CrX3 phases). Density functional theory (DFT) calculations support the structural stability and provide the magnetic and electronic properties of the 1D CrX2 chains.