Tunable magnetization and relaxor ferroelectric nature in cobalt-substituted tungsten bronze Ba4Nd2Fe2Nb8O30

The structural, magnetic and dielectric properties of tungsten bronze Ba4Nd2Fe2-xCoxNb8O30 (0 ≤ x ≤ 1) ceramics are investigated. The room-temperature ferromagnetic (FM) behavior with rather high FM transition temperature Tc can be observed in the Co-doped samples compared with the antiferromagnetic (AFM) interaction in the sample Ba4Nd2Fe2Nb8O30. The ferromagnetism can be understood in terms of spin canting of the AFM coupling of the Fe-based and Co-based sublattices via Dzyaloshinsky-Moriya interaction. All the samples exhibit the nature of relaxor ferroelectric. In addition, two thermally activated dielectric relaxations can be found in all the samples. The first one corresponds to a relaxor-like relaxation which obeys well Vogel-Fulcher relation, whereas the second one follows with Arrhenius Law and can be attributed to the localized hopping of electrons.