Room-temperature single phase multiferroic magnetoelectrics: Pb(Fe, M)(x)(Zr,Ti)((1-x))O-3 [M = Ta, Nb]

We describe extensive studies on a family of perovskite oxides that are ferroelectric and ferromagnetic at ambient temperatures. The data include x-ray diffraction, Raman spectroscopy, measurements of ferroelectric and magnetic hysteresis, dielectric constants, Curie temperatures, electron microscopy (both scanning electron microscope and transmission electron microscopy (TEM)) studies, and both longitudinal and transverse magnetoelectric constants alpha(33) and alpha(31). The study extends earlier work to lower Fe, Ta, and Nb concentrations at the B-site ( from 15%-20% down to 5%). The magnetoelectric constants increase supralinearly with Fe concentrations, supporting the earlier conclusions of a key role for Fe spin clustering. The room-temperature orthorhombic C-2v point group symmetry inferred from earlier x-ray diffraction studies is confirmed via TEM, and the primitive unit cell size is found to be the basic perovskite Z = 1 structure of BaTiO3, also the sequence of phase transitions with increasing temperature from rhombohedral to orthorhombic to tetragonal to cubic mimics barium titanate. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4790317]