MAGNETIC FORCE MICROSCOPY IMAGING OF DOMAIN-WALLS IN MAGNETITE

A magnetic force microscope was used to obtain high-resolution images of the stray magnetic field on the polished surface of a natural crystal of magnetite. These images allow us to model the nature of the magnetic domain boundaries which control the stability of magnetic remanence in multidomain grains. Analytic models of the stray field of domain walls are used to determine the magnetic fine structure of the wall. Two possible geometries of domain wall structure are considered, first that of a Bloch wall which does not lie parallel to the direction of magnetization in the adjacent domains, and secondly that of a Bloch wall with a Neel wall 'cap'. The experimental data favours the former wall geometry, although it is possible that bending of the wall can occur (forming a Neel wall cap) within about 20 nm of the grain surface.