INVESTIGATION OF FERRITE SURFACE TREATMENTS BY SPECTROSCOPIC ELLIPSOMETRY

The performance of Mn-Zn ferrites utilized for magnetic heads is very sensitive to any treatment that they are submitted to during the manufacturing process. We have therefore used ellipsometry to study the effects on the surface characteristics of single-crystal ferrites of different factors and treatments such as lapping, heat treatments, machining, and etching with an argon plasma. We have used both a spectroscopic ellipsometer and a two-wavelength ellipsometer. In this paper, investigation of argon plasma etching of the ferrite surface has demonstrated a clear evolution of the surface characteristics as a function of the etching duration. It is shown that a simple magnetic 'dead layer' model cannot explain the experiments in a satisfactory way. Our results have clearly shown that the information we can obtain using ellipsometry is related to surface roughness and chemistry. Further magneto-optical experiments of the ferrite surface tend to confirm this hypothesis. Ellipsometry appears to be a very powerful tool for investigating the surface of magnetic ferrites. Further work is under way to determine whether this method could be used as a routine inspection method in magnetic head manufacturing.