Exploring the effect of surface distortion, chemical passivation, and doping in thin film surfaces of K₂CoCl₆: A...

Highly spin-polarized magnetic materials have a great scope in spin-based device applications. In this study, the geometric, electronic structure, magnetism, and chemical bonding of bulk K₂CoCl₆ (KCC) and its bare, H- and O-passivated, and doped surfaces were investigated using first-principles DFT calculations. The results showed that KCC is ferromagnetic, with 83% spin polarization at the Fermi level. ELF and COHP calculations confirmed ionic bonding in Co-Cl with an average bond energy of -2.65 and an ICOBI value of 0.4. Among the three investigated surfaces (001), (011), and (111), the (001) surface presented the lowest surface energy and exhibited metallic properties. The H- and O-passivated surfaces exhibited a few lattice distortions. The O-passivated surface exhibited half-metallic properties. Aluminum (Al) doping of bare surfaces slightly modified the electronic structure and magnetism. The passivated and doped surfaces retained the bulk metallic characteristics. These findings provide a theoretical foundation for further experimental and theoretical investigations of K₂CoCl₆-based thin films and their potential application in future spintronic and spin-dependent electronic devices.