Characterization and microwave absorption of spinel MFe2O4 (M = Mg, Mn, Zn) nanoparticles prepared by a facile oxidation-precipitation process

Cation-substituted magnetite (MFe2O4, M = Mg, Zn, Mn) were prepared by a facile oxidation-precipitation process in an oxygen-free environment without autoclaves. By XRD, TEM, FESEM and EDS mapping analysis, the as-prepared MFe2O4 are characterized to be polycrystalline nanoparticles with spinel structures and regulated M/Fe ratios. Their electromagnetic properties are strongly dependent on the substitution of M2+. MnFe2O4 has higher saturation magnetization and increased coercivity in contrast to MgFe2O4 and ZnFe2O4. At the optimum absorbent thickness, ZnFe2O4 achieves a minimum reflection loss of -23.4 dB around 17.9 GHz, while MnFe2O4 exhibits a broad effective absorbing bandwidth covering 6.4 GHz in medium frequency ranges. The intense magnetic loss for MnFe2O4 and high dielectric loss together with effective electromagnetic impedance matching for ZnFe2O4 should be responsible for their enhanced microwave absorption performance.