Comprehensive investigation of the impact of transition metal doping on the opto-electronic and magnetic properties of Cs2NaAlF6 first principle study

Abstract

By employing first-principles calculations, we comprehensively investigate the magnetic and optoelectronic characteristics of pristine Cs2NaAlF6 (CNAF) double perovskites, as well as their behavior upon doping with transition metals Cr(Mn) at the Na-site. Our simulations employ the Wien2k code's full-potential linearized augmented plane-wave (FPLAPW) method, incorporating the generalized gradient approximation with on-site Hubbard correction (GGA + U) to accurately account for exchange and correlation interactions. The pristine Cs2NaAlF6 exhibits insulating properties, featuring a direct bandgap of 6.72 (10.50) eV as determined through GGA + U functional. However, upon substitutional doping of transition metals such as Cr and Mn into the Na-site of Cs2NaAlF6, impurity states emerge within the bandgap, thereby imparting semiconducting behavior to Cs2NaAlF6:Cr and Mn. This semiconducting nature holds immense significance for the development of next-generation spintronic devices. The substitution of Cr(Mn) at the Na-site results in partially filled d-orbitals, leading to magnetic moments (MMs) of 5 (6.03) μB. Furthermore, we investigate the optical properties (Real part (ε1(ω)), Imaginary part (ε2(ω)), extinction coefficient (k(ω)), refractive index (n(ω)), Reflectivity (R(ω)), energy loss function (L(ω)), and absorption (I(ω))) of both pristine Cs2NaAlF6 and Mn(Cr)-doped Cs2NaAlF6 across the photon energy range of 0–14 eV. Our analysis sheds light on the behavior of these properties as a function of photon energy. Our findings strongly establish that the substitutional doping of Cs2NaAlF6 with transition metals significantly enhances its electrical, magnetic, and optical properties. These enhancements position Cs2NaAlF6:Mn(Cr) as an outstanding candidate for optoelectronic and spintronic devices, thereby unlocking promising avenues for technological advancements.