Modelling damaged MFM tips using triangular charge sheets

A method is presented here which models a magnetically coated tip for use in magnetic force microscopy (MFM) using triangular and rectangular charge sheets to obtain analytical expressions for the three components of magnetic field and field gradient from the tip and hence the tip sensitivity function. The force and force gradient exerted on such a tip when scanned over a sample with a given magnetisation distribution are obtained using the convolution of the tip sensitivity function and the magnetisation distribution. Computed images are given which show that damaged tips can give higher resolution images than perfect uniformly coated tips. It is shown that it is not necessary to have a mechanically sharp tip in order to obtain a high resolution magnetic force image