First-principles investigations and Monte Carlo simulation of Ti and Cr-doped w-ZnO and (Ti,Cr) co-doped w-ZnO based magnetic semiconductors: Materials for spintronic applications

Abstract

This research paper investigates the electronic structure and magnetic properties of Ti-doped ZnO (Zn1−xTixO), Cr-doped ZnO (Zn1−xCrxO) and (Ti,Cr)-codoped ZnO (Zn1−xTix2Crx2O) systems with x = 0.08 and 0.12 dopant concentrations using density functional theory (DFT) combined with Monte Carlo simulation (MCS). Ab-initio calculations were based on spin-polarized density functional theory (SDFT) and were carried out within the framework of the GGA+U formalism. The study focuses on the impact of transition metal doping (TM = Ti, Cr) on the structural, electronic, and magnetic properties of the systems. The geometric analysis reveals that lattice parameters and bond lengths between atoms are influenced by the concentration of transition metal (TM) doping. The formation energies of all models indicate their energetic stability, making them suitable for synthesis in the laboratory. The results reveal that Ti-doped ZnO (ZTO), Cr-doped ZnO (ZCO), and (Ti,Cr)-codoped ZnO (ZTCO) systems exhibit a half-metallic behavior, with the Fermi level passing through localized impurity states. These systems behave as n-type semiconductors, with the Fermi level shifting into the conduction band. The presence of transition metal (TM) impurities in ZnO material enhances its magnetic moment and Curie temperature. Additionally, Monte Carlo simulation demonstrates that ZCO exhibits a Curie temperature above room temperature, consistent with experimental studies. Moreover, the co-doping of (Ti,Cr) in ZnO allows for the adjustment of the Curie temperature. At low temperatures, the hysteresis loop becomes more significant. These findings indicate the potential suitability of ZTO, ZCO, and ZTCO systems for spintronic applications.