Alloys of CoI₂ Nanoclusters Embedded in the PbI₂ Lattice Exhibiting High-Temperature Hysteretic Paramagnetic Transitions and Low-Temperature Diverse Magnetic Short-Range Ordering

Dilute magnetic semiconductors (DMSs) are crucial for various spintronic and magneto-optical applications, typically created by doping d- or f-orbital-based metal ions into wide bandgap nonmagnetic semiconductors. In this study, we synthesized Pb1–xCoxI2 (x = 0.05–0.14) alloys by doping PbI2 with Co2+ ions using a simple mechanochemical method and characterized their morphology, structure, thermal stability, and magnetic properties. The Co2+ ions in the alloys formed CoI2 clusters with dimensions less than 10 nm, homogeneously distributed within the PbI2 lattice. These alloys exhibited a paramagnetic phase transition with a thermal hysteresis loop at high temperatures (>370 K) and Co2+-content-dependent magnetic short-range ordering behaviors (spin glass, cluster glass, or superparamagnetism) at low temperatures (<15 K). The strong interactions between itinerant electrons and the localized 3d electrons of Co2+ ions indicate Pb1–xCoxI2 alloys, with characteristic behaviors observed in DMSs. This study demonstrates that mechanochemical synthesis is a facile and efficient method for preparing alloys of van der Waals crystals, offering precise control over alloy composition, particularly when dealing with reaction systems involving components with different soft–hard acid–base properties.