Broadband dielectric and Mössbauer studies of BaTiO3–NiFe2O4 composite multiferroics

A broadband dielectric investigation and Mössbauer studies were performed on 0.7BaTiO 3 –0.3NiFe 2 O 4 composite ceramics prepared from chemically obtained barium titanate and nickel ferrite powders. Dielectric spectroscopy revealed a Debye-type relaxation at frequencies between 10 GHz and 1 THz. The relaxation time slows down on cooling according to the Arrhenius law which can be attributed to the transformation of the system from the paraelectric to the ferroelectric phase through an intermediate relaxor state. The temperature dependence of the center shift of the Mössbauer spectrum was analyzed by applying Debye and Einstein models. Its deviation from these models can be attributed to the anharmonicity. It is also possible that the center shift is affected by the Fe atoms incorporated in BaTiO 3 lattice or at the interfaces between BaTiO 3 and NiFe 2 O 4 .