Synthesis, Structures, and Multiferroic Properties of Strontium Hexaferrite Ceramics

Abstract

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.