Quantitative field measurements from magnetic force microscope tips and comparison with point and extended charge models

In this article we present results and analysis from measurements of the field distributions from standard magnetic force microscope tips. These measurements are made using Lorentz microscopy and tomographic reconstruction techniques with the field reconstructed in a plane situated about 50 nm from the end of the magnetic force microscope (MFM) tip; this corresponds approximately to the sample plane in the MFM. By examination of the experimental results and comparison with simulated field distributions from point and extended charge distributions, we conclude that the magnetization configuration of the tip is best represented by an extended charge distribution and that the point pole approximation represents only, at best, the central part of the field distribution.