Synthesis, Structures, and Multiferroic Properties of Strontium Hexaferrite Ceramics

Simultaneous occurrence of large ferroelectricity and strong ferromagnetism has been observed in strontium hexaferrite (SrFe12O19) ceramics. Strontium hexaferrite powders with hexagonal crystal structures have been successfully synthesized through the co-precipitation precursor method using strontium nitrate and ferric nitrate as starting materials. The powders were pressed into pellets and then sintered into ceramics at a temperature range of at 1000°C to 1100°C for 1 h. The structure and morphology of the ceramics were determined using x-ray diffraction and field-emission scanning electron microscopy techniques. Clear ferroelectric hysteresis loops demonstrated large spontaneous polarization in the SrFe12O19 ceramics at room temperature. The maximum remnant polarization of the SrFe12O19 ceramic was estimated to be approximately 15 μC/cm2. The FeO6 octahedron in its perovskite-like hexagonal unit cell and the displacement of Fe3+ off the center of the octahedron are proposed to be the origin of electric polarization in SrFe12O19. In our experimental observations, the SrFe12O19 ceramic also revealed strong ferromagnetism at room temperature.