Development of M-type hexaferrite films for microwave device application

Abstract

M-type hexaferrite has been extensively used in microwave devices due to its large magnetocrystalline anisotropy, high magnetization and ferromagnetic resonance frequency over 50 GHz. Its high versatility in magnetic and dielectric properties with low losses in off-resonance frequency provides a significant important in non-reciprocal devices such as circulator, isolators, phase shifter and band filters. Substantial effort has been drawn to miniaturize these devices with self- biased ferrite materials. In the present dissertation, barium hexaferrite (BaM) powders with various substitution (Al, Ti, La, Co) were prepared. To understand the insight of the substitution, the powder were characterized by Raman spectroscopy, FTIR, and Mössbauer spectroscopy. As substituted powder were used to fabricate the screen printed thick films. The microstructural and magnetic properties of the films were measured in perpendicular and in-plane direction. Microwave properties of substituted sample were compared with pure BaM in X-band and Ku band. Apart from isotropic thick films, anisotropic microwave sintered thick films were also prepared under the presence of external magnetic field of 0.8 T. The effect of milling time on structural and magnetic properties of thick films were investigated.