Thickness and Composition Tailoring of K- and Ka-Band Microwave Absorption of BaCoxTixFe(12−2x)O19 Ferrites

The goal of this research is to investigate the electromagnetic and microwave absorption properties of M-type barium hexaferrites with chemical formula BaCoxTixFe(12−2x)O19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) in K and Ka band. Characterization techniques such as x-ray diffraction analysis and scanning electron microscopy were applied to confirm ferrite formation. The frequency dependence of the complex permittivity and complex permeability was studied for prepared ferrite samples in the frequency range from 18 GHz to 40 GHz. Factors such as the quarter-wavelength condition, impedance matching, high dielectric–magnetic losses, as well as ferromagnetic resonance were investigated to determine their contribution to the absorption characteristics. It was found that the quarter-wavelength (λ/4) model could be successfully applied to predict and understand the position as well as number of reflection peaks in the microwave absorption spectrum. The origin of the reflection loss peaks is explained and verified based on calculations of input impedance, loss tangent, and ferromagnetic resonance. Reflection loss analysis revealed that all six compositions exhibited reflection loss peaks (absorption >90%) at their matching thicknesses and frequencies. Therefore, these ferrites are potential candidates for use in electromagnetic shielding applications requiring low reflectivity in K and Ka band.