Probes for magnetic force microscopy imaging of soft magnetic samples

Magnetic force imaging of soft magnetic materials is often a challenge due to perturbing effects of the probe's stray field on the magnetic structure of the sample if the probe and the sample are too close. Especially with one commonly employed imaging mode, the lift mode, which is used in some commercial instruments, this problem is very severe, since very small tip-sample distances frequently occur during the imaging of the sample topography. In this study the effect is demonstrated by the imaging of arrays of micro-structured Permalloy films. It is shown that perturbations can be diminished by depositing a mechanical spacer on top of the probe's magnetic layer, which ensures that a minimum distance between the magnetic part of the probe and the sample is always kept.