Multiferroic property, dielectric response and optical behavior of filled tungsten bronze Ba4Nd2Fe2-xMnxNb8O30 (0 ≤ x ≤ 1) ceramics

In this paper, the structural, magnetic, dielectric, ferroelectric and optical properties of Mn doped tungsten bronze Ba4Nd2Fe2-xMnxNb8O30 (0 ≤ x ≤ 1) ceramics were investigated in detail. All the samples are of single phase with the tetragonal structure and the group space of P4bm. Compared with antiferromagnetism in pure sample, Mn-doped samples show a weak room-temperature ferromagnetic state. The observed ferromagnetism in Mn-doped ceramics can be understood in terms of the AFM coupling of Fe-based and Mn-based sublattices via Dzyaloshinskii-Moriya interaction. The relaxor ferroelectric nature can be demonstrated in the doped samples. The sample x = 0.5 exhibits a high storage energy density U of 1.06 J/cm3 and efficiency η of 94.3%. The low-temperature dielectric relaxation obeys well with Vogel-Fulcher relation and can be ascribed to the local polarization fluctuation, while the dielectric relaxation around 300 K follows with Arrhenius law and can be attributed to the localized hopping process of electrons. In addition, the optical band gap decreases from 2.64 eV to 2.49 eV with increasing the Mn concentration.