Electronic structure and multiferroic properties of (Y, Mn)-doped barium hexaferrite compounds

Highlights: • Electronic structure and multiferroic properties of (Y, Mn)-doped BaM compounds. • Enhanced Jahn-Teller distortions as increasing Mn-doping concentration. • Chemical shift of Mn²⁺→ Mn³⁺ and replacement of Mn²⁺,³⁺ for Fe³⁺ in BaM compounds. • Hard magnetic and a change in ferroelectric properties of BaM compounds. -- Abstract: We have systematically studied the crystal and electronic structures and the magnetic and electrical polarization properties of polycrystalline Ba_0.95Y_0.05Fe_12−xMn_xO₁₉ (denoted as BaYFe_12−xMn_xO₁₉) compounds with x = 0–2. The analyzes of X-ray diffraction patterns and Raman scattering spectra indicated their single phase in the M-type hexaferrite structure. With increasing x, the lattice constant a slightly increased while c decreased, which related to the Jahn-Teller effect. Though an increase of x reduced gradually magnetization in a range of 23–32 emu/g, the coercive force increased from 3.3 kOe for x = 0 to about 4 kOe for x = 0.5–2. The study of the electrical polarization properties proved the dependence of the shape of electric hysteresis loops on x and applied electric field. The samples with x = 0 and 0.5 exhibit a weak ferroelectricity with the maximum polarization of ~0.11 μC/cm² for x = 0, and of ~0.06 μC/cm² for x = 0.5. Meanwhile, the other samples showed nearly circular hysteresis loops, which are characteristic of conductive materials. Detailed investigations indicated an increase in leakage current when x increased. All of such phenomena are tightly related to the chemical shift of Mn²⁺ → Mn³⁺ and the replacement of Mn^2+,3+ for Fe³⁺ in BaYFe_12−xMn_xO₁₉. These oxidation states and the chemical shift of Mn have been confirmed upon analyzing X-ray absorption spectra.