  In this work, we explored theoretically the spatial resolution of magnetic
solitons and the variations of their sizes when subjected to a Magnetic Force
Microscopy (MFM) measurement. Next to tip-sample separation, we considered
reversal in the magnetization direction of the tip, showing that the magnetic
soliton size measurement can be strongly affected by the magnetization
direction of the tip. In addition to previous studies that only consider
thermal fluctuations, we developed a theoretical method to obtain the minimum
observable length of a magnetic soliton and its length variation due to the
influence of the MFM tip by minimizing the soliton's magnetic energy. Our model
uses analytical and numerical calculations and prevents overestimating the
characteristic length scales from MFM images. We compared our method with
available data from MFM measurements of domain wall widths, and we performed
micromagnetic simulations of a skyrmion-tip system, finding a good agreement
for both attractive and repulsive domain wall profile signals and for the
skyrmion diameter in the presence of the magnetic tip. Our results provide
significant insights for a better interpretation of MFM measurements of
different magnetic solitons and will be helpful in the design of potential
reading devices based on magnetic solitons as information carriers.
