Magnetoelectric Behavior of 0-3 Co/BaTiO 3-Composites

Reduction of Co3O4/BaTiO3 in forming gas followed by sintering in flowing nitrogen with carbon as oxygen getter was applied for the syntheses of magnetoelectric 0-3 Cox/(BaTiO3)1-x composites (x = 0.1 – 0.8). Phase pure BaTiO3 and a mixture of hexagonal and cubic Co were obtained with void-free embedding of micrometer-sized ferromagnetic Co particles in the ferroelectric BaTiO3 matrix. No incorporation of Co in the BaTiO3 matrix occurred and the nominal Co contents agree well with the experimental ones derived from Rietveld refinements and magnetic measurements. A complex field dependence of the magnetoelectric coefficient (αME) was found with at least two local maxima/minima and a pronounced hysteresis when the magnetic field and the polarization are oriented perpendicular to each other. The sample Co0.5/(BaTiO3)0.5 exhibits the largest αME values. The low-temperature phase transitions of BaTiO3 (tetragonal → orthorhombic → rhombohedral) can be observed in the temperature dependence of αME. In contrast to other composites the integral of αME and the magnetostriction of (hexagonal) cobalt show a distinctively different magnetic field behavior, which might be due to the additional presence of the cubic Co modification.