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 α33 and α31. 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 C2v 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.

We report the synthesis of single-phase Pb(Fe0.66W0.33)0.80Ti0.20O3 thin films by chemical solution deposition techniques on Pt∕Ti∕SiO2∕Si(100) substrates. At room temperature it showed relaxor behavior up to 50kHz frequency and almost linear dielectric constant for higher frequency. The dielectric diffusivity (γ=1.89) calculated from modified Curie-Weiss laws and nonlinear Vogel-Fulcher fitting implies relaxor characteristics of the films. Capacitance variation as function of applied field showed perfect “butterfly loops” for frequency (>10kHZ) at room temperature and for a full range of experimental frequencies near the freezing temperature (∼240K). Magnetization versus applied magnetic field displayed weak ferromagnetic properties.

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The coupling between magnetization and polarization in a room temperature multiferroic (Pb(Zr,Ti)O3 -Pb(Fe,Ta)O3 ) is explored by monitoring the changes in capacitance that occur when a magnetic field is applied in each of three orthogonal directions. Magnetocapacitance effects, consistent with P(2) M(2) coupling, are strongest when fields are applied in the plane of the single crystal sheet investigated.

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