Effect of La doping in the multiferroic compound BiFeO3

We have performed magnetization and magnetocapacitance measurements on ceramic samples of the multiferroic series Bi1-xLaxFeO3 for 0 <= x <= .0.25. We show that doping with La reduces the transition magnetic field from the spatially modulated state to a homogenous one and increases the magnetocapacitance, these effects being the strongest for x=0.15, which is the highest concentration for maintaining the non-centrosymmetric rhomboedral structure (R3c) of BiFeO3. For highest La content (x >= 0.17), analysis of the XRD patterns shows that the lattice symmetry gradually changes to orthorhombic (C222), giving rise to an enhancement of the latent magnetization and to a drop of the magnetodielectric constant. (C) 2011 Elsevier B.V. All rights reserved.