Magnetization distribution at the surface of Co-Cr films: magneto-optical, chemical and structural characterization

In magnetic high density recording media, the Wonnation is stared in the domain structure at the surface of thin films. Chemical, structural and magnetic properties at the surface plar an important role in the reading and writing process. In this thesis the results of an investigation on sputtered Co-Cr films, a most promissing high density recording medium, are presented. Special attention is pared to the upper 50 nm of the films, which is indicated as surface. It appeared from XPS and Auger experiments that the oxidized scale on room temperature annealed RF- and MRF-sputtered Co81Crl9 films was abaut 6 nm thick and consisted of three different larers. The topology as investigated br SEM, AFM and STM appeared to be stronglr related to the film's column morphology. The roughness amplitude varied trom 6 nm for the thinner films to 50 nm for the thick Co-Cr films. In order to investigate the magnetism at the surface of these films a combined optical and magneto-optical measurement srstem has been built, based on a polarizer film rotating analrser ellipsometer. The dielectric tensor elements were determined and appeared ta be stronglr dependent on the morphology of the film under investigation. It can be concluded from these results and those of others, that the Kerr rotation can be considered ta be linearlr dependent on the magnetization. Hrsteresis curves could be measured very accuratelr with the intensity technique. Major, minor and in-plane loops as weIl as the angle dependencr of the magnetizatian were studied br Kerr tracer and V SM. The differences between the measurement results obtained br bath methods can be explained br demagnetizing effects and film in- homogenities. A model was developed in order to calculate the influence of roughness, oxidatian- segregation surface larers and closure domains on the maximum readable infarmatian density .It can be concluded from the results of this calculation, that the recording performances of next generation media will be limited br the surface properties. A large surface loss is expected for linear bit densities in the order of 30 Mbit/m. "Closure damain loss" can be avoided br increasing the Q-factor of the thin film medium.