Structural evolution and microwave absorption properties of MnFe₂O₄/BaTiO₃ nanoparticle systems and their composites

Abstract In this study, MnFe₂O₄/BaTiO₃ nanoparticle systems were systematically investigated as microwave absorbers in the X-band (8–12.4 GHz). Nanoparticles were physically mixed at different weight ratios and examined both before and after annealing at 1100 C for 3 h. The microstructural and magnetic properties were evaluated using SEM, TEM, XRD, XPS, FTIR and M–H hysteresis measurements, respectively. Structural analyses revealed that the as-mixed samples consist of coexisting MnFe 2 O 4 and BaTiO 3 phases, while annealing induces an in-situ transformation into an Mn/Ti-substituted M-type barium hexaferrite phase. This phase evolution leads to a significant increase in saturation magnetization and coercivity, indicating a transition toward harder magnetic behavior. Microwave absorption performance was evaluated using reflection loss measurements. The non-annealed 50 MnFe 2 O 4 –50 BaTiO 3 composite exhibits the best absorption performance, with a minimum reflection loss (RL) of approximately − 23 dB at 10.8–11.0 GHz. In contrast, annealed samples show reduced absorption efficiency, with minimum reflection loss values in the range of − 10 to − 16 dB. These results demonstrate that enhanced magnetic hardness does not necessarily improve microwave absorption in MnFe 2 O 4 /BaTiO 3 -based absorbers.