Multiferroic properties of Bi<inf>1/2</inf>Sr<inf>1/2</inf>FeO<inf>3</inf>

Polycrystalline Bi12 Sr12 Fe O3 was synthesized by solid state reaction method. Powder x-ray diffraction pattern of the sample was fitted using a noncentrosymmetric rhombohedral crystal system of space group R3c. The sample was found to be free from any secondary phases. This single phase material exhibits simultaneously ferrimagnetism and ferroelectricity with magnetic and electrical Curie transitions at TCM =745 K and TCE =465 K, respectively. Origin of this spontaneous magnetic order is discussed using the superexchange interaction between Fe ions. The observed ferroelectric polarization is explained based on the spontaneous ordering of 6 s2 lone pair electrons of Bi3+ ions and a possible coexistence of charge-ordering of site- and bond-centered types. © 2009 American Institute of Physics.