Molecule‐Induced Huge d‐p Overlap Enhances Superexchange Interaction for Room‐Temperature In‐Plane Magnetism and Giant Magneto Band‐Structure Effect in Ferromagnetic Clusterphene

Abstract The discovery of 2D van der Waals XY ferromagnets is a vital task to access excellent topological spin textures, yet remains a longstanding challenge due to low critical temperatures ( T C ) and weak in‐plane magnetic anisotropy. Here, a novel 2D ferromagnetic clusterphene, (Cr 3 As 2 ) 2 Cp 3 (Cp = cyclopentadienyl), by using Cr 3 As 2 Cp 3 cluster self‐assembly with Cp as linker is proposed. Via first‐principles calculations, it is demonstrated that an enhanced ferromagnetic superexchange interaction between the d orbital is achieved through a salient overlap onto the molecular frontier orbitals of the Cp ligand, producing a room‐temperature T C . The (Cr 3 As 2 ) 2 Cp 3 clusterphene characterizes an ideal XY ferromagnet and a giant magneto band‐structure (GMB) effect. Functional groups and element modifications are also introduced to effectively manipulate the magnetic anisotropy and the GMB effect. The results showcase that 2D magnetic cluster‐assembled clusterphenes fuel a wide range of possibilities for exploring XY magnetism in reduced dimensions.