Effect of combined Ca/Ti and Ca/Nb substitution on the crystal and magnetic structure of BiFeO3

• Published in: Journal of magnetism and magnetic materials Vol. 491; p. 165561
• Main Authors: Khomchenko, V.A., Karpinsky, D.V., Ivanov, M.S., Franz, A., Dubkov, S.V., Silibin, M.V., Paixão, J.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2019; Elsevier BV
• Subjects: Antiferromagnetism; BiFeO3; Bismuth ferrite; Calcium ions; Crystal defects; Crystal structure; Displacements (lattice); Ferroelectric materials; Ferroelectricity; Ferromagnetism; Magnetic materials; Magnetic properties; Magnetic structure; Multiferroics; Niobium; Organic chemistry; Perovskites; Spin cycloid; Substitution reactions; Spin cycloid; BiFeO3; Magnetic materials; Crystal structure; Multiferroics
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2019.165561

[Display omitted] •Ca/Ti and Ca/Nb substitutions modify the antiferromagnetic structure of BiFeO3.•The cycloidal structure → canted structure transformation is studied.•Lattice defects contribute to the instability of the cycloidal antiferromagnetic order. Herein, we report on the crystal structure, magnetic and local ferroelectric properties of the Bi1−xCaxFe1−xTixO3 and Bi1−xCaxFe1−x/2Nbx/2O3 perovskites prepared by a solid state reaction method. It has been found that the Ca2+/Nb5+-containing series is characterized by a narrower concentration range (x ≤ 0.2) over which the acentric R3c structure specific to the pure BiFeO3 can be stabilized. The compositional variation in the critical concentration defining the polar/nonpolar (R3c/Pnma) phase boundary can be understood as related to the chemical modification-induced changes in the lattice spacing diminishing the stability of the a−a−a− tilting in favor of the a−b+a− one. Both the Ca2+/Ti4+ and Ca2+/Nb5+ substitutions ensure the suppression of a cycloidal antiferromagnetic order, thus leading to the formation of a weak ferromagnetic polar state. While this effect is proven to be associated with a composition-driven reduction in polar displacements, lattice defects are supposed to contribute to the instability of the cycloidal spin arrangement.