Multiferroic Cobalt Ferrite-Lead Iron Tungstate Composites

The paper presents dielectric, magnetic and magnetoelectric properties of multiferroic bulk composites based on CoFe2O4 ferrite and Pb(Fe2/3W1/3)O-3 relaxor. X-ray diffraction analysis and scanning electron microscopy observations of ceramic samples revealed two-phase composition and fine grained microstructure with uniformly distributed ferromagnetic and ferroelectric phases. Dielectric permittivity measured in a temperature range 218-773 K at frequencies of 10 Hz-2 MHz exhibits high and broad maxima attributed to dielectric relaxation. The hysteresis determined in a temperature range 4-393 K for magnetic field changing from -80 kOe to 80 kOe is typical of hard magnetic materials. Saturation magnetizations and coercivities were found to decrease with increasing temperature. The courses of zero field cooled and field cooled magnetization versus temperature curves measured in the temperature range 4-393 K imply spin glass behavior of the ferrite and antiferromagnetic transition of the relaxor at low temperatures. The ferrite-relaxor composite shows high magnetoelectric voltage coefficient which distinctly increases with increasing frequency of ac magnetic field and is slightly higher for higher ac and dc magnetic fields.