Magnetic force microscopy of domain wall fine structures in iron films

This work investigated the micromagnetic structure of single crystal iron films by means of magnetic force microscopy (MFM) and Kerr microscopy. The investigated samples were epitaxially grown Fe films on a GaAs substrate. The film thickness varied between 30 and 500 nm. With the Kerr microscope it was possible to localize efficiently the domain walls in iron films. These walls were subsequently imaged by MFM with a high resolution. The MFM was used to observe the fine structure of a Bloch wall. Experimental results were compared with the calculated MFM response that was based on a two-dimensional, micromagnetic model describing the magnetic structure of an asymmetric Bloch wall. Both theory and experiment demonstrated the influence of the stray field of the tip on the wall structure. We could observe symmetric Néel walls and cross tie walls in a 30 nm iron film after reducing the sensitivity of the MFM tip. In order to achieve this state the tip was demagnetized by an external field.