Structural phase separation and optical and magnetic properties of BaTi_1−xMn_xO₃ multiferroics

Our work studies the influences of the Mn doping on structural characterization and optical and magnetic properties of BaTi_1−xMn_xO₃ (x = 0.0–0.12) prepared by conventional solid-state reaction. Detailed analyses of XRD patterns and Raman scattering spectra indicate an incorporation of Mn dopants into the Ti sites of BaTiO₃ host lattices, and the tetragonal-hexagonal transformation taking place at a threshold concentration of x_c ≈ 0.01. An increase of Mn-doping content in BaTi_1-xMn_xO₃ introduces more electronic levels associated with lattice defects and Mn ions to the forbidden gap and thus reduces luminescent intensity in the visible region. Magnetic data recorded at room temperature reveal that all the samples exhibit ferromagnetic order, and there is a phase separation in magnetism as varying x values. Particularly, the samples with x = 0.5–0.7 have a coexistence of two ferromagnetic phases with different coercivities, which are associated with tetragonal and hexagonal Mn-doped BaTiO₃ structures. The nature of ferromagnetism is explained by means of the results of structural and optical analyses, where Mn³⁺ and Mn⁴⁺ ions play a crucial role.