The crystal structure and multiferroic properties of single-phase (Bi0.9La0.1)FeO3-Ba(Fe0.5Nb0.5)O-3 ceramics were investigated. The rhombohedral-type structure of 1.0(Bi0.9La0.1)FeO3) was transformed to a monoclinic-type structure for the 0.5(Bi0.9La0.1)FeO3-0.5Ba(Fe0.5Nb0.5)O-3) composition. It shows the coexistence of ferroelectricity and magnetism at room temperature, represented by a high dielectric constant with ferroelectric hysteresis and clear magnetic hysteresis behavior. The authors propose that the solid solution of A and B site cations according to their ionic radii and valence state stabilized the spontaneous polarization and magnetization at room temperature. (c) 2007 American Institute of Physics.