Ferromagnetic resonance study on magnetic homogeneity in spin-sprayed NiZn ferrite films highly permeable at gigahertz frequencies

Ferromagnetic resonance (FMR), including standing spin-wave resonance (SWR) modes, were measured in NiZn ferrite films, which have high permeability even up to the gigahertz range. They were prepared from an aqueous solution by spin spray ferrite plating at 90/spl deg/C. The perpendicular field FMR spectra exhibited SWR modes whose line separation had linear dependence on spin wave number, deviating from the quadratic behavior. This indicated that the films have inhomogeneous distribution of magnetization perpendicular to film plane, and have different magnetic surface anisotropies between the inner and outer surfaces of the respective films. The in-plane field FMR spectra revealed no SWR mode. A possible model is proposed to explain the features not only of the FMR spectra, but also of the initial permeability spectra measured on the films.

I. Introduction

NiZn ferrite films prepared by spin-spray ferrite plating from an aqueous solution at 90 °C have high permeability even up to the gigahertz range [1]. The films directly deposited onto a strip line on an epoxy printed circuit board suppressed the conduction noise up to 3 GHz strong enough for actual utilization as gigahertz noise suppressors [2]. Adding to the oxidizing solution (which raises ) not only enhanced natural ferromagnetic resonance frequency (a criterion for usable frequency) in the ferrite plating, but also increased film deposition rate up to 67 nm/min without degrading the film quality [3]. This is quite advantageous for applying to the noise suppressors. In this study, we measured X-band ferromagnetic resonance (FMR), including standing spin-wave resonance (SWR) modes [4], in order to investigate the magnetic homogeneity in two types of the films, one prepared using the adjusting solution of (called hereafter -used film), the other prepared without adding (called conventional film).