10-nm resolution by magnetic force microscopy on FeNdB

Magnetic force microscopy (MFM) images of rapidly quenched FeNdB are presented. The magnetic domain structure as observed by MFM consists of elongated, polyhedral-shaped domains imaged by measuring forces smaller than 10−9 N at distances ranging from 20 to more than 200 nm. The domain transition regions, which are quite sharp and well defined, often show a double-peaked structure with a peak-to-peak distance of 10 nm. At force sensor tip-to-sample separations larger than 90 nm only a single peak is observable. It has to be assumed that the relevant effective magnetic volume of the force sensing tip is considerably smaller than the geometric dimensions as determined by scanning electron microscopy in order to understand this 10-nm resolution