In the last decade since its development, magnetic force microscopy[l] has emerged as a workhorse in imaging magnetic structures at the sub-micron length scales. It possesses the desirable attributes of robustness, straightforward implementation and a fairly well characterized image contrast formation. In recent years, we have successfully implemented MFM in the presence of a highly controlled external magnetic field.[2] Using this technique, it is possible to follow the sample’s magnetic evolution at various points along it’s magnetization curve. Further, by using standard software implementation, the images can be presented as an animation of the micromagnetic process. We applied this technique to study a variety of slow varying dynamics of magnetic systems, including the dc erasure of thin film recording media[3], the mechanisms of moment rotation and reversal, and the domain wall motion nanostructured magnetic elements[4,5].

In this talk, I will review the rudiments of the technique and show the “dynamics” of the magnetization of cobalt and Permalloy alloys interacting with external fields.