Magnetic and ferroelectric domain structures in BaTiO3-(Ni0.5Zn0.5)Fe2O4 multiferroic ceramics

BaTiO3-(Ni0.5Zn0.5)Fe2O4 composites prepared by co-precipitation were investigated. The macroscopic magnetic properties derived from the magnetic phase (low coercivity, almost no M(H) hysteretic behavior and high permeability) are preserved in the composite. The dielectric properties are strongly influenced by interface phenomena (Maxwell-Wagner), due to the local electrical inhomogeneity. At low frequencies, the composites present thermally activated conductivity and relaxation, while at 1MHz permittivity of around 500 and tan delta < 8% is obtained at room temperature. The multiferroic character was demonstrated at nanoscale by the presence of the magnetic and ferroelectric domain structure in the same region. Imprint polarisation in the regions corresponding to the ferroelectric phase is found, as result of an internal electrical field created at the interfaces between the (Ni,Zn)-ferrite and BaTiO3 regions.