Investigation of the response of a new amorphous ferromagnetic MFM tip coating with an established sample and a prototype device

Abstract A new type of amorphous ferromagnetic MFM tip coating has been used to obtain high-resolution images of domain wall structures in a magnetically soft amorphous thin film and a prototype recording head. The new tip coating has a composition close to that of commercial METGLAS®2605SC (FeSiBC) amorphous ribbon and is produced by RF-sputtering on to Nanosensors™ Si probes. A cross-tie wall found in an amorphous alloy thin film of composition Co91Nb6Zr3 (at%) was taken as an established sample. Detailed study of the periodicity of the main wall, and features of the sub-structure under a variety of tip conditions, established the robustness of the images obtained. This is an important step in the use of MFM on soft magnetic materials. For comparison, images of the same section of cross-tie wall have been obtained with a commercial CoCr tip, showing an unacceptable degree of image perturbation. Having established the conditions for robust imaging, a prototype recording head produced from two layers of Co91Nb6Zr3 with an SiO2 isolation interlayer was successfully imaged by MFM. A classic closure domain structure adjacent to the gap was observed, in conjunction with pinned walls along the edges of the device where the etching is imprecise.