The Use of Micro-Mechanical Techniques, AFM and MFM to Access Surface Deformation in Multilayered Thin Films

Abstract

Micro-mechanical techniques were used to introduce tailored deformations to a pre-written magnetic disk. Atomic force microscopy (AFM) and magnetic force microscopy (MFM) were then used to map out the topography of the indentations and their effects on the underlying magnetic layers. The tailored deformation included pyramidal and conical indents, scratches and micro-wear tracks. The extent of topographic damage assessed by AFM was correlated with the carefully monittored normal and tangential forces of the microindenter. Sub-surface ‘damage’ was assessed by MFM, monitoring for loss of resolution in pre-written magnetic data tracks in the underlying magnetic layer. From the combination of micro-mechanical and MFM techniques, we have found that magnetic bit contrast degradation can be mechanically introduced by either physical damage or by shape modification of the magnetic coating. The indentation and scratch tests both confirm that static pressure alone is not sufficient to cause the magnetic bit degradation; however, wear is capable of introducing bit damage at much lower contact pressures. Surface corrugation generated by the wear process alters the geometry of the magnetic coating, thereby causing magnetic bit pattern degradation. Good correlation was found between the degree of disk surface damage and the degree of magnetic bit contrast degradation.