Magnetic and dielectric characterization of xBiFeO3:(1-x)SrFe12O19 multiferroic composites

Multiferroic composites xBiFeO3:(1-x) SrFe12O19 (0.5 ≤ x ≤ 1, Δx = 0.1) were produced by mixing powders of BiFeO3 and SrFe12O19 obtained by high energy ball milling assisted with heat treatment. To study their multiferroic properties, the ferromagnetic, dielectric and magnetodielectric behavior was evaluated for each composite. The composites were produced using powders of BiFeO3 and SrFe12O19 that were mixed, pressed at 800 MPa, and sintered at 700 °C for 4 h. XRD analysis confirms the presence of both ferroic phases, BiFeO3 and SrFe12O19, and small amounts of the secondary phase, Bi2Fe4O9 (mullite). The quantity of this secondary phase increases with the concentration of strontium hexaferrite. The remanent magnetization values are 17.9 emu/g and 2.54 emu/g for x = 0.5 and x = 0.9, respectively. The coercive field does not change with the composition; it exhibits a nearly constant value of 5.5 kOe for all the samples containing strontium hexaferrite. The addition of strontium hexaferrite produces diminution of the relative permittivity (ξr) and dielectric losses (tan δ). At 5 MHz, the composite with x = 0.9 shows the highest relative permittivity (16.78), and a diminution of dielectric loses of 43.88% due to the higher resistivity of the strontium hexaferrite. The magnetodielectric measurements showed an increase in the relative permittivity of the composites due to a reduction of the resistivity in agreement with the Maxwell-Wagner behavior when a magnetic field was applied. This study show evidence for magnetoresistive behavior by pure bismuth ferrite at room temperature, which has not been previously reported. •BFO–SHF composites were synthesized by assisted high-energy ball milling.•Multiferroic composites showed improved ferromagnetic and ferroelectric behavior.•Bismuth ferrite shows magnetoresistive behavior at room temperature.•A change in the space charge polarization produces a magnetocapacitive response.•The magnetocapacitance observed does not have a magnetoelectric origin.