Spatial and force resolution of magnetic force microscopy in current imaging

Magnetic force microscopy (MFM) can be used to image current distributions in current leads of sub-micron dimensions. Here we present a systematic stu dy about the spatial and force resolution of such currents. In the case of force resolution, we studied the least measurable magnetic force of MFM for different sample currents. The analysis of images from parallel Al conduct ing plates are combined with those from force-distance curves and finite el ement calculations. Several interacting regimes between the magnetic tip an d the currents are found and interpreted. It is shown that model calculatio ns are necessary even for qualitative image interpretation. Then spatial re solution in the range of 100 nm can well be obtained and quantitative studi es of current distributions on widths of 10 nm resolution are possible in s pecial cases. The approach is demonstrated in imaging the current distribut ion in superconducting Bi2Sr2CaCu2Ox single crystals.