Preparation and Characterization of Barium Hexaferrite (BaFe12O19) Thick Films For Micro/Millimeter Wave Device Application

Abstract

M-type barium hexaferrite (BaM) thick films have gained considerable attention for high frequency device applications such as circulators, isolators, phase shifters and microwave absorbers. The characteristic features of BaM such as high magnetocrystalline anisotropy (Ha), high saturation magnetization (M), moderate coercivity (Hc) and high ferromagnetic resonance (FMR) frequency. FMR frequency can be tuned by varying intrinsic parameters such as Ha and M. Henceforth, the main objective of the present work is realization of screen printed BaM thick films with minimal porosity, tunable Ha and Ms. The screen printing technique is capable to produce films of few 100 µm thick, which overcomes the limitation to grow thick films by other deposition techniques such as RF sputtering and pulsed laser deposition (PLD) technique. To prepare BaM thick films, a paste of BaM powder and binder were screen printed on alumina substrate. Firstly, BaM powders were prepared by solid-state reaction and the effect of processing parameters such as powder size and sintering temperature on the structural properties is studied. To tune the Ms and Ha, variation of Fe/Ba mole ratio and suitable substitution for Ba and Fe ions are adopted. Further, BaM thick films with variable Ms and Ha are developed for their potential use in tunable high frequency applications. Various techniques were used to examine the structural, microstructural, magnetic properties and high-frequency characteristics of BaM powders and screen printed thick films. The magnetic properties of non-substituted and substituted BaM thick films suggest a possible candidate for microwave applications.