The magnetodielectric effect in BaTiO3–SrFe12O19 nanocomposites

Abstract

A nanoscale composite consisting of 30 vol% magnetic strontium hexaferrite SrFe₁₂O₁₉ embedded in a high dielectric permittivity matrix of BaTiO₃ has been produced by the spark plasma sintering method. The morphology and phase composition were characterized by transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) techniques. TEM micrographs indicate that no considerable grain growth occurs and different strained regions were formed by the sintering process. XRD investigations show no evidence of a chemical reaction between the constituents. The dielectric properties of such a nanocomposite were investigated versus temperature (50–300 K), frequency (100 Hz to 100 kHz) and magnetic field (0–5.6 Tesla). A magnetodielectric (MD) effect was detected in the whole studied temperature range. Above 150 K the occurrence of sharp magnetodielectric resonances around 1 kHz leads to a considerable enhancement of the effect. At temperatures below 150 K a positive MD effect was detected which is independent of the frequency.