Electron spin resonance study and improved magnetic and dielectric properties of Gd–Ti co-substituted BiFeO₃ ceramics

Polycrystalline BiFeO₃ (BFO), Bi_0.90Gd_0.10FeO₃ (BGF), Bi_0.90Gd_0.10Fe_1−xTi_xO₃ (x = 0.03–0.10; BGFT_x) ceramics were prepared via solid state reaction method. X-ray diffraction studies reveal R3c symmetry for BFO and BGF samples and coexistence of R3c + Pn2 ₁ a symmetries for BGFT_x samples. The change in line width of Raman modes indicates the structural distortion and substitution of dopants ions in the BFO lattice. Magnetic studies show weak ferromagnetism in BGF and BGFT_x samples as a result of Gd³⁺–Fe³⁺, Gd³⁺–Gd³⁺ interactions and imbalance created between two antiparallel Fe³⁺ spin sublattices by Ti substitution. The maximum remnant magnetization of 0.141 emu/g is observed for BGFT_x=0.10 sample. Further, electron spin resonance study confirms the weak ferromagnetism of BGFT_x samples, associated with small grains and increase in anisotropy of particles distribution as found during SEM studies. UV–Visible absorption spectra in the spectral range from 1.6 to 3.5 eV showed one d–d crystal field transition and two charge-transfer transitions with optical band gap variation in visible region. Improved dielectric properties with very low values of dielectric loss have been observed for BGF and BGFT_x samples.