Effect of oxygen defects in tuning the half-metallic and optical nature of Sr2CoXO6 (X=Mo & W): A first-principles study

Abstract

Over the last few decades, double perovskites have been studied extensively because they exhibit exotic properties, such as magnetoresistance, ferroelectricity, superconductivity, half-metallicity, multiferroic, and many more. In this article, we used density functional theory based first-principles calculations to understand the effect of oxygen deficiency on the structural, electronic, optical and spin-oriented properties of cubic Sr2CoXO6 (X = Mo & W). The pure structures exhibit half-metallicity along with ductile nature. The band structures (using GGA-PBE) suggest that the conduction band and the valence band of both structures are overlapped in both spin-state after introducing oxygen defects, meaning that point defects in the oxygen-site make the structure lose its half-metallic nature. But, using HSE06 exchange correlation functional, we obtain half-metallic characteristics of Sr2CoWO5.75 structure. Further, the broad peak of absorption and optical conductivity of both structures occur in the UV region, and they dissipate with increasing energy. We obtain plasmon peaks from the loss function at 13.26 eV for Sr2CoMoO6 and 13.561 eV for Sr2CoWO6. Due to oxygen defects in the UV region, the peaks of absorption coefficient, reflectivity, optical conductivity, and plasmon peaks are red-shifted. We claim that these structures have a huge probability in spintronics and optoelectronic applications, although oxygen vacancies may reduce some applicability.