Separation of the first- and second-order contributions in magneto-optic Kerr effect magnetometry of epitaxial FeMn/NiFe bilayers

The influence of second-order magneto-optic effects on Kerr effect magnetometry of epitaxial exchange coupled FeMn/NiFe-bilayers is investigated. A procedure for separation of the first- and second-order contributions is presented. The full angular dependence of both contributions during the magnetization reversal is extracted from the experimental data and presented using gray scaled magnetization reversal diagrams. The theoretical description of the investigated system is based on an extended Stoner-Wohlfarth model, which includes an induced unidirectional and fourfold anisotropy in the ferromagnet, caused by the coupling to the antiferromagnet. The agreement between the experimental data and the theoretical model for both the first- and second-order contributions are good, although a coherent reversal of the magnetization is assumed in the model.Comment: 6 pages, 7 figures, submitted to J. Appl. Phy

Tuning exchange bias

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.The exchange bias shift of the hysteresis loop, HE, in antiferromagnetic/ferromagnetic layer systems can be easily controlled (within certain limits) by cooling in zero field from different magnetization states above the antiferromagnetic Néel temperature, TN. This indicates that for moderate cooling fields, HE is determined by the magnetization state of the ferromagnet at TN, and not by the strength of the cooling field

A PNR study of the off-specular scattering during the asymmetric magnetization reversal in an exchange-biased Co/CoO multilayer

We report on the observation of the effects of exchange bias on the magnetization reversal processes in a [Co/CoO/Au]20 system using polarized neutron reflectometry (PNR). The focus in this study is the investigation of the off-specular scattering of neutrons from magnetic domain structures during the magnetization reversal. In a previous PNR study on the same system, an asymmetry in magnetization reversal has been observed on opposite sides of the same hysteresis loop. For the decreasing field branch, the reversal was found to be dominated by domain wall motion of domains directed parallel or antiparallel to the applied field. In contrast, the reversal on the increasing field branch was characterized by rotation of magnetization. A significant loss of intensity was found for the specular reflected neutrons, while off-specular scattering experiments reveal that this magnetization reversal is not determined by coherent rotation but rather by a breaking up into smaller domains with different orientations.NRC publication: Ye