A cation-exchange approach to tunable magnetic intercalation superlattices.

Abstract

Tailoring magnetic ordering in solid-state materials is essential for emerging spintronics^1,2. However, substitutional lattice doping in magnetic semiconductors is often constrained by the low solubility of magnetic elements^3-5, limiting the maximum achievable doping concentration (for example, less than 5%) and ferromagnetic ordering temperature⁶. The intercalation of magnetic elements in layered two-dimensional atomic crystals (2DACs) without breaking in-plane covalent bonds offers an alternative approach to incorporate a much higher concentration of magnetic atoms (for example, up to 50%) beyond the typical solubility limit. However, commonly used chemical and electrochemical intercalation methods are largely confined to a few isolated examples so far. Here we report a general two-step intercalation and cation-exchange strategy to produce a library of highly ordered magnetic intercalation superlattices (MISLs) with tunable magnetic ordering. Monovalent transition-metal cations Cu⁺ and Ag⁺, divalent magnetic cations Mn²⁺, Fe²⁺, Co²⁺ and Ni²⁺, and trivalent rare-earth cations Eu³⁺ and Gd³⁺ have been successfully incorporated into group-VIB 2DACs, including MoS₂, MoSe₂, MoTe₂, WS₂, WSe₂ and WTe₂, and group-IVB, -VB, -IIIA, -IVA and -VA 2DACs, including TiS₂, NbS₂, NbSe₂, TaS₂, In₂Se₃, SnSe₂, Bi₂Se₃ and Bi₂Te₃. We show that these MISLs can be prepared with tunable concentrations of magnetic intercalants, enabling tailored magnetic ordering across a diverse array of functional 2DACs, including semiconductors, topological insulators, and superconductors. This work establishes a versatile material platform for both fundamental investigations and spintronics applications.