VARIABLE MAGNETIC-FIELD MAGNETIC FORCE MICROSCOPY OF THE MAGNETIZATION REVERSAL IN EPITAXIAL IRON(111) THIN-FILMS

The magnetization reversal in epitaxial. iron [1 1 1] films has been s tudied using MFM with in situ magnetic fields and, in addition, correl ated with macroscopic data obtained by conventional magnetometry. Due to the crystallographic orientation and growth-related strain of the f ilms, they do not have an in-plane magnetic easy axis which results in a fine stripe domain pattern in zero magnetic field. The observed zer o field stripe period and the critical thickness for stripe formation in the films are in approximate agreement with theory. The magnetizati on reversal in these films can be described in terms of two distinct r egimes: the 'fast' regime in which the in-plane magnetization of magni tude approximately half the saturation magnetization reverses in a nar row field range around the coercive field (of approximately 100 Oe), a nd the 'slow' regime at higher fields where the in-plane magnetization gradually increases toward saturation along the applied held. The sal ient features in the 'fast' regime shown by the MFM data are subtle: t he positions of the stripes do not change indicating that the out of p lane magnetization components are not altered; and the only clearly ob servable change is a reduction in the number of forks or defects in th e stripe pattern. As the held is further increased through the 'slow' regime, the stripe domain period decreases. In addition, in the high f ield region where the bulk hysteresis loop data indicate the magnetiza tion to be reversible, the MFM data clearly indicate that the magnetiz ation process is irreversible with the average stripe width observed t o be smaller in decreasing the held after saturation. (C) 1998 Publish ed by Elsevier Science B.V. All rights reserved.