MICROMAGNETIC AND MFM STUDIES OF A DOMAIN-WALL IN THICK (110)FESI

A 180 degrees domain wall on a {1 1 0} surface of a 0.3 mm thick cryst al of FeSi (3.25% Si), and containing a Bloch line, has been studied b y magnetic force microscopy (MFM) with particular attention to disturb ance by the probe. A technique for distinguishing the contributions to the MFM signal arising from the undisturbed structure and from the di sturbance to that structure, by repeating the observations with probe moment reversed, is discussed. Valid to first order, and applicable on ly to mild reversible perturbations, it is used to compare the observe d wall structure with that of a micromagnetic model. Asymmetry in the MFM signal is consistent with the presence of a Neel cap that closes t he flux to one side of the wall at the surface. Scanning by the probe sometimes created! (or destroyed) kinks in attractive wall sections. T hese kinks are identified as junctions between lengths of wall having a common Bloch core but opposite Neel cap orientations. Comparison is made with a micromagnetic model of such a kink. The kinks and the Bloc h line could be moved by scanning, depending on the polarisation and f lying height of the tip. (C) 1998 Elsevier Science B.V. All rights res erved.