Effect of heat treatment on microwave absorption properties of Ni–Zn–Mg–La ferrite nanoparticles

• Spinel structure Ni–Zn–Mg–La ferrite has been first prepared by sol–gel auto combustion route.
• The effects of heat treatment on structure and microwave properties for the ferrite are investigated.
• Electromagnetic loss and reflection loss property of the ferrite system are greatly improved by increasing annealing temperature.

Spinel structure Ni–Zn–Mg–La ferrites have been prepared by the sol–gel route and investigated as a radar absorbing material (RAM) in a frequency range of 1–18 GHz. The structure and morphological studies on the nanoparticles of the ferrites have been carried out using X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The complex permeability and complex permittivity are measured by a network analyzer. The electromagnetic wave loss and microwave absorbing property are studied as a function of frequency, annealing temperature and thickness of the absorber. The results indicate that electromagnetic wave loss of the ferrite only annealed at 850 °C shows two peaks. The reflection loss varies with the change of the annealing temperature. The absorber annealed at 850 °C exhibits the best microwave absorbing properties, which is suitable for microwave absorption materials.