Titanium atoms dimerization phenomenon and magnetic properties of titanium-antisite (Ti-O) and chromium doped rutile TiO2, ab-initio calculation

摘要

The ab-initio calculations based on the Korringa Kohn Rostoker approximation approach combined with coherent potential approximation (KKR-CPA), were used to study the magnetic properties of the titanium anti-site (Ti-O) and chromium (Cr) doped TiO2. In the considered systems, we used different concentrations for Ti-O defect and Cr doping. In TiO2(0.98)(Ti-O)(0.02), the obtained results indicate that Ti-O is a donor having half-metal behavior. Ti-O[3d] band is located at the Fermi level, although isn't 100% polarized, the ferromagnetic (FM) state is verified as being more stable than disordered local moment (DLM) state. For Ti0.98Cr0.02O2 the Cr doping introduced new states which give the material half-metallic feature. The majority spin of Cr impurities are located at the Fermi level and the conduction electrons around the Fermi level are 100% spin polarized. This indicates the stability of (FM) state. Moreover, in Ti0.98Cr0.02O2(0.98)(Ti-O)(0.02), the top of the valence band is shifted to lower energy compared to pure TiO2, and the n-type of TiO2 is verified. The majority spin of Cr[3d] are located at 0.025 Ry close to the Fermi level. The predicted Curie temperatures (Tc) were calculated using the mean field approximation (MFA) and we predicted that Ti-O defect in Cr doped TiO2 makes Tc higher. This kind of defect makes the material useful for spinotronics's applications and devices. (C) 2016 Elsevier Ltd. All rights reserved.