Structure, impedance spectroscopy, and magnetic properties of nanostructured composites (1-x)CoFe2O4–xPbTiO3

Abstract

The article presents a comprehensive investigation of the crystal structure, impedance spectra, magnetic, magnetodielectric, and magnetoresistive properties of (1-x)CoFe2O4–xPbTiO3 composites with varying concentrations (х = 0, 0.2, 0.4, and 0.6). The study also examines the effects of applying a uniaxial pressure of 1 GPa to the synthesized powders using Bridgman anvils. Our findings reveal that the synthesis of these composites results in the formation of an additional phase, lead hexaferrite PbFe12O19, which exhibits multiferroic properties. Additionally, the coherent scattering region of the components is significantly reduced after mechanical activation. Notably, the real part of the resistivity ρ′(ω) of nanostructured CoFe2O4 ceramics increases eightfold at T = 240 °C. The composites demonstrate significant magnetoresistance at room temperature, reaching up to 250 %. The study also reveals that the signs of the magnetodielectric MD(B) and magnetoresistive coefficient MR(B) vary with the frequency of the measuring field for certain concentrations. Using the first-order reversal curve (FORC) method, it was observed that after nanostructuring CoFe2O4 through mechanical activation, the interaction field Hu shifts from ± 0.6 kOe to ± 0.8 kOe, while the coercive field Hc increases from 1.05 kOe to 5 kOe. Moreover, the two-dimensional FORC maps of the composites show increased complexity, due to the formation of additional magnetic phases.