Spectral manifestation of the transformation of the crystal structure with substituted Bi by Sm in Bi1-xSmxFeO3 and their magnetic properties

Nano-sized BiFeO₃, BiFeO₃ doped with different amounts of Samarium, and SmFeO₃ were prepared by the solution combustion method. The obtained compounds have the general formula Bi_1-xSm_xFeO₃, where 0 ≤ x ≤ 0.2. To investigate and clarify the modifications in the crystal structure of the synthesized samples, X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy were used. The compounds with gradual substitution of Bi³⁺ by Sm³⁺ are characterized by the sequence of the structural transformations from the rhombohedral phase R3c to the orthorhombic phase Pbnm. The concentration range corresponding to the coexistence of the rhombohedral (R3c) and orthorhombic (Pbnm) phases is observed in the interval 0.1 < x < 0.2. The compound Bi_0.85Sm_0.15FeO₃ has significant remanent magnetization, hysteresis loop and coercivity compared to other samples due to the coexistence of two crystalline phases orthorhombic (Pbnm) and rhombohedral (R3c) in a percentage ratio of 92 % and 8 %, i.e. a transformation of the crystalline phases occurs.