Controllable magnetic properties and enhanced microwave absorbing of Ba2Mg2Fe12O22@Ni0.5Zn0.5Fe2O4/multi-walled carbon nanotubes composites

Abstract Multiferroic Y-type Ba2Mg2Fe12O22 (BMFO) hexaferrite, spinel Ni0.5Zn0.5Fe2O4 (NZFO) ferrite, and multi-walled carbon nanotubes (MWCNTs) ternary composites have been successfully fabricated via one-step sol-gel method followed solvothermal method. The electron microscopy analysis exhibits that platelet-like BMFO and quasi-spherical NZFO grains are surrounded by dispersed MWCNTs. The magnetic and microwave absorption (MA) performances are hugely associated with the mass ratio of BMFO to NZFO phase. The saturation magnetization of composites increases from 24.2 to 69.0 emu/g, while permittivity declines apparently with increasing NZFO content. It is easy to infer that the addition of NZFO phase may be beneficial to balance the relative permittivity and permeability of BMFO@NZFO/MWCNTs, which can endow the strong reflection loss of the composites. When the mass ratio of BMFO to NZFO is 3:1, the absorber shows the minimum reflection loss of −36.1 dB at 14.3 GHz with a relatively thin thickness of 1.8 mm, and effective absorption bandwidth (less than −10 dB) of 4.1 GHz. When the mass ratio is reduced to 1:3, the minimum reflection loss reaches to −40.8 dB at 10.6 GHz with an absorber thickness of 2.5 mm, and the effective absorption bandwidth is achieved in the frequency range from 8.0 to 11.9 GHz which covers almost the whole X band (8.0–12 GHz). For the two composites mentioned above, the effective absorption bandwidth covers almost the entire frequency range by changing the absorber thickness from 1 mm to 5 mm. Very interestingly, the effective absorption band shifts to the low frequency by adding NZFO, attributing to adequate exchange-coupling interaction between BMFO and NZFO phases. These mentioned results demonstrate that composites consisting of multiferroic Y-type hexaferrite, spinel ferrite and carbon material have a potential application in high-performance MA materials integrating vigorous absorption intensity, broad absorption bandwidth and thin thickness.