Temperature‐Induced Structural Evolution and Magnetism in Self‐Intercalated V1+xSe2 Nanoplates

Abstract 2D van der Waals (vdW) magnets provide the ideal platform for studying magnetism at low dimensions, where the magnetic properties can be further tuned by intercalating magnetic species and manipulating their stoichiometry and local atomic configuration. However, achieving stoichiometric intercalated 2D magnets necessitates precise control of growth parameters to avoid local compositional variations, which fosters phase coexistence that significantly impacts magnetic properties. Here a comprehensive scanning transmission electron microscopy (STEM) examination of the structural evolution in chemical vapor deposition (CVD)‐grown self‐intercalated V 1+x Se 2 nanoplates is shown, exploring their response to annealing temperature variations and the subsequent influence on magnetic properties. By combining ex situ and in situ post‐growth annealing, the rearrangement of intercalants is directly observed at the interlayer and identify a structural phase transition of the nanodomains embedded in the VSe 2 matrix from V 3 Se 4 to a V 5 Se 8 structure occurring at ≈250 °C. The interlayer reconstruction is manifested by a positive‐to‐negative cross‐over in the magnetoresistance and an upturn in resistivity at low temperatures. The results provide new ways for tailoring 2D vdW magnets through post‐growth thermal annealing.