Ferrite Magnetic-Anisotropy Field Effects on Inductance and Quality Factor of Planar GHZ Inductors

Abstract

Abstract-Planar gigahertz (GHz) inductors were fabricated based on high crystalline-anisotropy Zn 0.13 Co 0.04 Ni 0.63 Fe 2.2 O 4 (Zn-Co-Ni ferrite) and Ba 3 Co 2 Fe 24 O 41 (Co 2 Z hexaferrite) and characterized for inductance (L) and quality (Q) factor. The planar ferrite inductors show an L of 4.5 nH (Zn-Co-Ni), 5.6 nH (Zn-Co-Ni + low H k and f FMR Co 2 Z:), and 4.8 nH (Zn-Co-Ni + high H k and f FMR Co 2 Z:) at 2 GHz. The corresponding L-densities are 18.0, 22.4, and 19.2 nH/mm 2 , which are greater than 16.8 nH/mm 2 of the air-core inductor. With respect to the Q factor, the air-core and ferrite inductors exhibit Q factors of 6.7 (air-core), 4.8 (Zn-Co-Ni), 2.8 (Zn-Co-Ni + low H k Co 2 Z), and 4.0 (Zn-Co-Ni + high H k Co 2 Z) at 2 GHz. The tan δ µ of the ferrites caused a reduction in the Q factor. Nevertheless, the high H k and f FMR Co 2 Z ferrite inductor demonstrates a higher Q factor than that of the low H k and f FMR Co 2 Z inductor. It is, therefore, suggested that high resistivity, anisotropy, magnetization ferrite can produce large L density and Q factor GHz inductors.