Theoretical investigation of transition metal (Cr, Fe)-Doped AlN in a rocksalt structure: A DFT study on physical properties

This study presents first-principles computations to explore the structural, electronic, optical, elastic, vibrational, and thermodynamic properties of Aluminum Nitride (AlN) doped with the transition metals Chromium (Cr) and Iron (Fe) in the rocksalt structure. Using spin-polarized density functional theory (DFT) within the CASTEP code, we applied GGA-PBE, GGA + U, and HSE06 approximations for exchange-correlation functions. Our results reveal that Cr doping transforms AlN into a dilute magnetic semiconductor (DMS), while Fe doping induces a transition to a metallic state. Both Al₀.₇₅Cr₀.₂₅N and Al₀.₇₅Fe₀.₂₅N exhibit strong covalent bonding, contributing to enhanced hardness. The substantial increase in static dielectric constant and refractive index suggests strong optical responses. Furthermore, our analysis confirms the mechanical and dynamic stability of these compounds. Al₀.₇₅Cr₀.₂₅N is a promising candidate for electronic and spintronic applications, whereas Al₀.₇₅Fe₀.₂₅N, with its high conductivity, is well-suited for magnetic storage devices and electrical contacts. Our findings for AlN are consistent with prior theoretical and experimental data, while the results for Al₀.₇₅Cr₀.₂₅N and Al₀.₇₅Fe₀.₂₅N offer novel insights for future research.