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 manuf acturing process. We have therefore used ellipsometry to study the eff ects on the surface characteristics of single-crystal ferrites of diff erent factors and treatments such as lapping, heat treatments, machini ng, and etching with an argon plasma. We have used both a spectroscopi c ellipsometer and a two-wavelength ellipsometer. In this paper, inves tigation of argon plasma etching of the ferrite surface has demonstrat ed a clear evolution of the surface characteristics as a function of t he etching duration. It is shown that a simple magnetic 'dead layer' m odel cannot explain the experiments in a satisfactory way. Our results have clearly shown that the information we can obtain using ellipsome try is related to surface roughness and chemistry. Further magneto-opt ical experiments of the ferrite surface tend to confirm this hypothesi s. Ellipsometry appears to be a very powerful tool for investigating t he surface of magnetic ferrites. Further work is under way to determin e whether this method could be used as a routine inspection method in magnetic head manufacturing.