Fe₃₀Co₇₀/Co/Co_xFe_3-xO_4- nanocomposite with multiple magnetic exchange resonance mechanisms and large magnetic loss available for microwave absorption application

Soft magnetic alloys are widely studied and reported as a type of important microwave absorption (MA) materials, while their magnetic losses are limited. In this paper, a multiphase composite strategy of the soft magnetic alloys, hard magnetic metals, and hard magnetic ferrites is adopted for increasing the magnetic loss. Then, three-phase Fe50Co50/CoxFe3-xO4-delta/gamma-Fe2O3 (FC31), three-phase Fe30Co70/Co/CoxFe3-xO4-delta (FC22), and three-phase CoxFe3-xO4-delta/Co3O4/Co (FC13) nano-composites are prepared by a simple thermal decomposition process of FeC2O4 and CoC2O4 in vacuum. The crystal structure, surface composition, vibration of chemical bonds, morphology, micro-structure, and static magnetism are characterized by XRD, XPS, FTIR, Raman, SEM, TEM, and SQUID, respectively. The electromagnetic (EM) parameters are measured in 2-18 GHz by a vector network analyzer. Based on the measured EM parameters, the calculated magnetic loss tangents (tan delta(m)) are over 0.5 in a wide frequency band of 8-18 GHz for the FC22/paraffin absorber, showing that the tan delta(m) can be increased dramatically through the multiphase composite strategy. Benefiting from the increased tan delta(m), an effective absorption bandwidth of 7.0 GHz is achieved for the FC22/paraffin absorber at a thin thickness of 1.45 mm, exhibiting great application advantages in the MA field.