Frequency-tunable microwave absorption via balanced impedance matching in Zn0.35Ni0.65Fe2O4/Ni-Cu multiphase ferrite composites

To address the challenges of impedance mismatch and limited absorption bandwidth in ferrite-based microwave absorbers, a one-step oxygen-deficient sintering process was employed to fabricate Zn 0.35 Ni 0.65 Fe 2 O 4 /Ni-Cu multiphase composites. This approach effectively regulates Cu 2+ substitution for Ni 2+ /Zn 2+ in the ferrite lattice while modifying the Ostwald ripening process, synergistically enhancing dielectric and magnetic losses. The pure Zn 0.35 Ni 0.65 Fe 2 O 4 exhibits a broad low-frequency absorption of 5.6 GHz (3.4–9.0 GHz, covering the entire C-band). Notably, the Zn 0.35 Ni 0.65 Fe 2 O 4 /Ni-Cu composite achieves a remarkable minimum reflection loss (RL min ) of −35 dB along with an effective absorption bandwidth (EAB) of 4.7 GHz. Consequently, this work provides both a facile synthesis methodology and mechanistic insights for designing high-performance electromagnetic materials with multiband operability.