First principles investigation on the electronic, magnetic and optical properties of Bi0.8M0.2Fe0.9Co0.1O3 (MÂ =Â La, Gd, Er, Lu)

Our results show that electronic, magnetic and optical properties in BFCO could be effectively modulated by rare-earth element dopings. The La- and Er-dopings reduce the band gaps to 1.72 and 0.81 eV and convert the systems to half-metallic, while the Lu and Gd dopings convert the systems to metallic. The static dielectric function ε1(0) is equal to 9.0, 7.0, 7.4, 9.2 and 10.5 for the pristine Er-, La-, Gd- and Lu-doped BFCOs respectively. Moreover, the 4f electronic of rare-earth elements especially Lu (4f14) and Gd (4f7) have obvious effects on the dielectric constant. The absorption spectra also show an advanced optical response in the visible range for BLuFCO and BGdFCO, and their optical transitions originate mainly from O 2p valance bands to the Fe 3d or Lu/Gd 4f conduction bands. These results suggest that BLuFCO and BGdFCO thin films could be considered as potential materials for photovoltaic devices.171