First principle investigations of the Pbnm phase BiFeO, BiFeMnO and BiXFeMnO (XBFM) (X = Ce, Gd, Lu).

The structural, magnetic, electronic and optical properties of Pbnm BiFeO (BFO), BiFeMnO (BFM), BiXFeMnO (XBFM) (X = Ce, Gd, Lu) have been investigated by the first principles within the PBE+U scheme. It is shown that the dopant Mn in the B sites and Ce (Gd, Lu) in the A sites improves the crystalline quality. The magnetic moments of BiCeFeMnO (CBFM) and BiGdFeMnO (GBFM) are 10 and 16 which mainly arises from the strongly localized unpaired 4 f electrons of Ce and Gd, 3 d electrons of Mn and Fe. While, as BFM, the magnetic moment of BiLuFeMnO (LBFM) is 9 indicating no effect on the magnetization is made by Lu for its full 4 f states. The densities of states of the five systems hint that CBFM is metallic and BFM, GBFM, LBFM are still semiconductors. The metallic properties of CBFM arise from the hybridization between Ce-4 f and Mn-3 d states which leads the Mn states to be split into and lowering the bottom of the conduction band to cross the Fermi level. Furthermore, we also study the optical properties of Pbnm BiFeO (BFO), BiFeMnO (BFM), BiXFeMnO (XBFM) (X = Ce, Gd, Lu). In this work, the optical properties including the absorption spectrum, loss function, refractive index and reflectivity spectrum are discussed in detail. [ABSTRACT FROM AUTHOR]