Computational and experimental study of the doping of Bi₂Fe_4-xM_xO₉ (M=Ga, Al, or Ge)

Transition metal oxides have attracted interest due to the range of physical properties which are of scientific interest and of interest due to their potential applications. Here we report a study into the doping of Bi₂Fe_4-xM_xO₉. Doping the system with M=Ga, Al, or Ge, allows us to modified the magnetic moment on the iron site and alter the ionic and magnetic order of the material. The structure itself consists of metal oxide polyhedron that are seen throughout the entire crystal. Two edge sharing octahedron are connected to a tetrahedron in all locations, where the bismuth sits outside of these polyhedrons. Monte-Carlo simulations have been performed using the Metropolis algorithm to reduce the Coulomb energy - taking into account ionic radii and charge - to determine whether the M sit on the tetrahedron sites, or the octahedron. As well as using the Heisenberg Model to model the overall magnetic moment of the crystal. Crystals of the material with the three options for M have been grown, and we also report results from magnetization and x-ray measurements that test the simulations.