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•Mesoporous CoFe2O4 and CoLa0.12Fe1.88O4 are prepared by nanocasting method.•Mesoporous structure plays an important role in the high reflection loss.•La doping further improves the microwave absorption of CoLa0.12Fe1.88O4.
Low-density ordered mesoporous CoFe2O4 (OCFO) and CoLa0.12Fe1.88O4 (OCLFO) are prepared by nanocasting method using mesoporous silica SBA-15 as a hard-template. The crystal structure, surface chemical state, magnetic properties and electromagnetic parameters are characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption measurement, X-ray photoelectron spectroscopy, physical property measurement system and vector network analyzer. The results show that all the samples formed a single phase with cubic spinel structure. Meanwhile OCFO and OCLFO possess a highly ordered mesostructure. Comparing with particle CoFe2O4 (P-CFO), OCFO with high specific surface area exhibits lower magnetic saturation (Ms), higher imaginary part of complex permittivity (ε′′) and imaginary part of the complex permeability (μ′′). The minimum reflection loss (RL) of OCFO reaches −27.36dB with a matching thickness of 3.0mm. The enhancement of the microwave absorbing performances of OCFO can be mainly attributed to the good impedance matching, high electromagnetic wave attenuation and multiple reflections of electromagnetic wave originated from the ordered mesoporous structure. The Ms of OCLFO decreases after La3+ doping, while the specific surface area, coercivity value, ε′′ and μ′′ of OCLFO increase. The minimum RL of OCLFO reaches −46.47dB with a thickness of 3.0mm, and the effective absorption frequency bandwidth reaches 4.9GHz.