The effect of tip type and scan height on magnetic domain images obtained by MFM

In the last few years there has been a considerable expansion in the application of Magnetic Force Microscopy (MFM). MFM images the stray field from the sample, offers excellent lateral resolution (similar to 10 nm) and requires minimal sample preparation. The interaction between the stray field from the sample and from the sensing tip depends on the shape of the tip, the composition and-thickness of its coating and the scan height above the sample. The effects of tip type and scan height on the MFM image are reported for a Nd-Fe-B specimen composed of a few large crystallites of similar orientation. The observed structures of order greater than or equal to 1 mu m are discussed in the context of established models for the domain structure of strongly uniaxial materials. Unexpected fine magnetic structure approximate to 25 nm is reported.