Magnetoelectric behaviour of 0-3 Co/BaTiO3 composites

Reduction of Co3O4/BaTiO3 in forming gas followed by sintering in flowing nitrogen with carbon as an oxygen getter was applied for the synthesis of magnetoelectric 0-3 Co-x/(BaTiO3)(1-x) composites (x = 0.1-0.8). Phase pure BaTiO3 and a mixture of hexagonal and cubic Co were obtained with a void-free embedding of micrometer-sized ferromagnetic Co particles in the ferroelectric BaTiO3 matrix. No detectable 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 (alpha(ME)) was found with at least two local maxima/minima plus a pronounced hysteresis when the magnetic field and polarization are oriented perpendicular to each other. The sample Co-0.5/(BaTiO3)(0.5) exhibits the largest alpha(ME) values. The low-temperature phase transitions of BaTiO3 (tetragonal -> orthorhombic -> rhombohedral) can be observed in the temperature dependence of alpha(ME). In contrast to other composites, the integral of alpha(ME) and the magnetostriction of (hexagonal) cobalt show a distinctively different behavior, which might be due to the additional presence of the cubic Co modification.

Automated summary

The study successfully synthesized magnetoelectric Co/BaTiO3 composites using reduction and sintering techniques, achieving seamless embedding of ferromagnetic Co in the ferroelectric BaTiO3 matrix. Complex magnetoelectric effects and temperature-dependent phase transitions of BaTiO3 were observed.