Structure, magnetic and microwave absorption properties of NiZnMn ferrite ceramics

The Ni x Zn y Mn 1-x-y Fe 2 O 4 ferrite ceramics were prepared by the sol–gel auto-combustion method. X-ray diffraction, scanning electron microscopy, infrared spectroscopy, vibrating sample magnetometer and vector network analyzer were used to characterize the microstructure and magnetic properties of the samples. The results show that only cubic spinel structure was detected by XRD in all sintered samples except the sample Zn 0.4 Mn 0.6 Fe 2 O 4. The lattice parameter decreases monotonously with Ni content and simply increases with Mn content, which is stemmed from the change of ionic radii. The saturation magnetism increases when Ni content x is less than 0.4. The initial permeability has the largest value at x = 0.2, which fits in with the mechanism of domain wall motion. The Curie temperature increases with the increase of x due to the enhanced A-B interaction. The highest T c is 505℃ for Ni 0.8 Zn 0.2 Fe 2 O 4 ferrite. The effect of adding Mn elements on the magnetic properties depends on the content of Zn. When y is 0.2, the magnetic parameters (M s and μ i ) increase with Mn content. However, when y is 0.4, they decrease because of redistribution of cations and the increase of α-Fe 2 O 3. In addition, all samples with Ni elements show strong electromagnetic wave absorption capability in 2–13 GHz range, the minimum RF is −25.36 dB at 4.74 GHz for the Ni 0.6 Zn 0.2 Mn 0.2 Fe 2 O 4 samples.