Probes for magnetic force microscopy (MFM) were prepared by pinning iron-filled multi-wall carbon nanotubes (CNTs) to conventional cantilever force sensors. The ends of the high aspect ratio iron nanowires within the nanotubes can be considered as stationary effective magnetic monopole moments which opens the possibility of quantitative stray field measurements in a straightforward manner.
Since the spatial resolution of an MFM image strongly depends on the distance between the effective sensor pole and the sample surface, we tailor CVD-grown Fe-filled CNTs by locally removing parts of the carbon shells using electron beam induced oxidation in humid environment. The carbon shell thickness can be reduced dramatically without altering the magnetization of the embedded single domain iron nanowire.
Approaches for direct CVD growth of aligned single iron-filled CNTs on cantilever sensors will be discussed.