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Complex magnetization behavior in Bi1-xCaxFe1-xMnxO3 multiferroics near the R3c/Pnma phase boundary: A revised study
Authors: Khomchenko, V.A.
Ref.: J. Phys. Chem. Solids 218, 113984 (2026)
Abstract: The crystal and magnetic structure as well as the magnetic properties of Bi1-xCaxFe1-xMnxO3 multiferroics near the R3c/Pnma phase boundary were investigated using a series of polycrystalline samples with x = 0.12, 0.17, and 0.22. X-ray diffraction confirms a single-phase rhombohedral (R3c) structure for x = 0.12 at room temperature, whereas samples with x = 0.17 and 0.22 exhibit a coexistence of rhombohedral and orthorhombic (Pnma) phases. All samples display weak ferromagnetic behavior at 400 K, with remnant magnetization that decreases as the temperature drops, indicating a change in the magnetic structure. Samples with higher Ca/Mn content show a re-emergence of remnant magnetization at low temperatures. Metamagnetic anomalies are observed, particularly in the rhombohedral phase, with the threshold field depending on both temperature and Ca/Mn concentration. Neutron diffraction data suggest that the R3c phase contributes to spontaneous magnetization near room temperature, while the Pnma phase remains collinear antiferromagnetic throughout the studied temperature range (2-400 K). The temperature-driven evolution of the magnetic structure in the R3c phase likely involves a reversible transition from a canted to a cycloidal antiferromagnetic state as temperature decreases, governed by the competition between ferroelectric distortions and out-of-phase oxygen octahedra rotations.
