First-principles investigation of the structural, electronic, magnetic and optical properties of magnetic semiconducting alloys Zn1-xNixO in the zinc-blende, rocksalt and wurtzite phase

Abstract

n this study, using spin-polarized density functional theory (DFT) calculations, a detailed investigation is conducted into the structural, electronic, magnetic and optical properties of Zn_1–xNi_xO ternary alloys in the wurtzite, zinc-blende and rocksalt crystal phases. The calculated lattice parameters show a a slight nonlinear variation with Ni concentration, indicating a minor deviation from Vegard’s law in the intermediate composition range. Electronic structure calculations reveal that all investigated alloys preserve their semiconducting nature throughout the entire composition range, although both the type and value of the band gap depend strongly on the crystal phase and Ni content. Charge density analysis suggests that pure ZnO exhibits a partially covalent bonding character, that gradually weakens as the concentration of Ni increases. The magnetic results show that NiO possesses a total magnetic moment of 4 μB per unit cell in the wurtzite phase and 2 μB per unit cell in the zinc-blende and rocksalt phases. Optical investigations indicate that both alloying and phase transitions significantly modify the optical response of the material. Notably, the alloys exhibit a strong absorption over a broad photon energy range, with the rocksalt phase showing the highest absorption. The static refractive indices for various compositions and crystal structures are also reported.