Crystal structure and properties of Bi1 − x Ca x FeO3 and Bi1 − x Ca x FeO1 − x Ti x O3 solid solutions

Abstract

Systems of solid solutions Bi1 − x Ca x FeO3 (I) and Bi1 − x CaxFeO1 − x Ti x O3 (II) have been obtained and their properties have been studied using neutronography and Mössbauer spectroscopy; magnetization and permittivity have been measured. It is shown that an increase in the concentration of calcium ions in system I for x > 0.2 changes rhombohedral distortions of a unit cell (space group R3c) to tetragonal distortions (space group I4/mcm), while rhombohedral distortions in system II for x > 0.2 are replaced by orthorhombic distortions (space group Pnma). Analysis of the crystal structure has revealed strong anisotropy in vibrations of Bi and O ions in system I compounds. Systems I and II are characterized by G-type antiferromagnetic ordering of magnetic moments. In system II, spontaneous magnetization associated with the Dzyaloshinskii-Moriya interaction has been detected. According to Mössbauer spectroscopy data, iron ions in compounds I and II are in the trivalent state and charge compensation occurs due to the formation of oxygen vacancies. The permittivity increases with the calcium concentration.