Search for increased performance in bifeo₃: Effect of a-Site substitution

Investigation of crystal structure, dielectric, magnetic and local ferroelectric properties of the diamagnetically- substituted Bi_1-xA_xFeO_3-x/2 (A= Ca, Sr, Pb, Ba; x= 0.2, 0.3) polycrystalline samples has been carried out. It has been shown that the heterovalent A²⁺ substitution result in the formation of oxygen vacancies in the host lattice. The solid solutions have been found to possess a rhombohedrally distorted perovskite structure described by the space group R3c. Piezoresponse force microscopy have revealed signs of existence of the ferroelectric polarization in the samples at room temperature. Magnetization measurements have shown that the magnetic state of these compounds is determined by the ionic radius of the substituting elements. A- site substitution with the biggest ionic radius ions has been found to suppress the spiral spin structure of BiFeO3 giving rise to the appearance of room-temperature weak ferromagnetism. The result indicates possible way for improving multiferroic properties of BiFeO_3- based magnetic ferroelectrics.