Microwave absorption properties of nanostructured nickel ferrite

The present paper discusses the development, characterization and microwave absorption properties of nanostructured nickel ferrite and the influence of loading of the frequency selective surfaces (FSS) on microwave absorption. Synthesis of the material was done by a sol-gel mediated auto-combustion technique and phase purity was determined by X-ray diffraction studies. As prepared nickel ferrite of crystallite size of 12.0 nm and the calcined sample of 36.0 nm were used for further studies. The complex permittivity, permeability and the reflection loss of the materials were measured in X-band (8.2 GHz to 12.4 GHz) and the properties are compared with their crystallite size. Simulations have been carried out using Ansoft HFSS (High Frequency Structure Simulator) microwave software of single and double square geometry for nickel ferrite to obtain the maximum absorption with large band width. Single layer nickel ferrite absorber of thickness 3 mm, loaded with double-square FSS has given the reflection loss (RL) of -12.5 dB at 9.6 GHz and -10 dB with a bandwidth of 2.0 GHz. The loading of FSS increased the reflection loss of nickel ferrite with 12.0 nm crystallite size whereas a broadening in the bandwidth of absorption was observed for nickel ferrite of larger crystallite size.