Substitution-induced changes in the structure, vibrational, and magnetic properties of BiFeO3

To address practical progress and prospective applications of BiFeO₃, particularly in the development of data storage devices, we substituted it with the perovskite BaTi_0.9Zr_0.1O₃ to form the system (1 − x)BiFeO₃-(x)BaTi_0.9Zr_0.1O₃, limiting x to the range of 0–0.4. We prepared these compositions using the solid-state reaction method, highlighting the correlation between their structure, vibrational properties, and magnetic response. X-ray diffraction and Raman scattering spectra reveal the structural transition from the R3c rhombohedral to Pmm cubic with increasing the content of BaTi_0.9Zr_0.1O₃. Mössbauer spectroscopy investigation indicates that the substitution of Fe³⁺ ions with Ti⁴⁺ and Zr⁴⁺ weakens the Dzyaloshinskii–Moriya (DM) interaction. Thus, the DM interaction becomes subordinate to the exchange interaction in the G-type antiferromagnetic order of Fe³⁺ ions within the BFO structure, potentially suppressing the cycloidal spin configuration in the samples x = 0.1, 0.2, and 0.3. The mean hyperfine magnetic fields decreased with the increasing (x) of BaTi_0.9Zr_0.1O₃, and a paramagnetic phase was observed for x = 0.4. The decrease of quadrupole splitting/shift (ΔE_Q/2ε) for x = 0.1, 0.2, and 0.3 indicates a transition toward a higher-symmetry environment around Fe³⁺ due to the substitution. This result proves the structural transition from the R3c rhombohedral to Pmm cubic observed by X-ray diffraction and Raman spectroscopy as the content of BaTi_0.9Zr_0.1O₃ increases. Using Rietveld refinement data of X-ray diffraction, the calculation of the tilt angle (ω) reveals a decrease in the level of the rhombohedral structure. For compositions exceeding x = 0.1, the decrease in ω with the substitution rate leads to a reduction in remanent magnetization. However, the enhancement of remanent magnetization (M_r ∼ 0.34 emu g⁻¹) was observed for x = 0.1. Moreover, hysteresis loops for the compositions x = 0.1 and 0.2 exhibit smaller field coercivity at 2 K compared to 300 K, which could identify the presence of magnetoelectric coupling in this system.