Phase transformations in multiferroics Bi1–xCaxFe1–xMnxO3

Abstract

The crystal structure and the magnetic properties of multiferroics Bi_1–xCa_xFe_1–xMn_xO₃ (x ≤ 0.22) have been studied. It has been found that the stoichiometric compositions undergo a crystal-structure transformation from the rhombohedral (space group R3c) polar phase (x ≤ 0.18) to the orthorhombic (space group Pnma) nonpolar phase (x ≥ 0.20) via a two-phase structural state. The polar phase is antiferromagnetic at x < 0.10 and exhibits a metamagnetic behavior. The polar (x ≥ 0.10) and nonpolar phases are weak ferromagnets at room temperature with a spontaneous magnetization close to 0.07 emu/g (x = 0.18 and 0.22). A decrease in temperature leads to the transition to a state close to an antiferromagnetic one.