Enhanced magnetic properties and densification of SrFe12O19/Fe3O4 hard/soft composites via cold sintering process

Magnetic ferrite composites are widely used in high-frequency applications due to their unique combination of magnetic and electrical properties. In this study, SrFe 12 O 19 /Fe 3 O 4 (SFO/FO) hard/soft composite ceramics were synthesized using the cold sintering process (CSP) and characterized to evaluate their structural, magnetic and electrical performance. X-ray diffraction confirmed the coexistence of SFO and FO phases, while magnetic measurements revealed hybrid behavior combining hard and soft magnetic characteristics. The addition of FO phase improved particle dispersion and compaction, as reflected in the enhanced relative density (90-92%) and Vicker hardness (3.0-3.7 GPa). Annealing changed the phase of Fe 3 O 4 to α-Fe 2 O 3 and reduced the pores, which made the composite materials more compact. These effects resulted in improved coercivity (∼4 kOe), remanence, and squareness ratio (∼0.5), with an optimized energy product (BH max ) of 0.80 MGOe observed for the 5%FO composite. Electrical analysis showed an increase in AC conductivity with higher FO content, while annealing reduced conductivity to ∼10 -7 S/cm at 1 kHz, ensuring sufficiently high impedance suitable for high-frequency applications. The successful synthesis of these composites via CSP at low temperatures demonstrates its feasibility as a method for investigating phase formation and magnetic interactions in ceramic nanocomposites. • SrFe 12 O 19 /Fe 3 O 4 hard/soft ceramic composites synthesized via low-temperature CSP. • Enhanced microstructure and compaction of the composite with Fe 3 O 4 addition. • Improved exchange coupling between SrFe 12 O 19 and Fe 3 O 4 through annealing. • Optimized structural, magnetic, and electrical properties with CSP and annealing.