Micromagnetic modeling of magnetization reversal of Fe/Cr/Co exchange coupled multilayers (abstract)

Abstract

Multilayers consisting of Fe/Cr/Co were prepared under molecular beam epitaxial condition on MgO substrates. These kind of multilayers exhibit different types of exchange coupling with respect to the Cr spacer thickness. We have studied the samples by means of magnetooptic Kerr microscopy as well as Brillouin light scattering and additional MOKE characterization. The investigations were performed on samples with homogeneous Cr spacer thickness and also on wedge type samples. From light scattering experiments we were able to locate the ferromagnetic and the antiferromagnetic coupled regions in the wedged sample. We obtained a switching field for the antiferromagnetic coupled layers of the order of 100 kA/m. Detailed MOKE studies revealed an fourfold inplane anisotropy with collinear axes of Co and Fe layers. In order to get insight in the magnetization reversal process in such multilayers, we studied the magnetic domain dynamics simultaneously to the measurement of hysteresis loops using magnetooptic Kerr microscopy. Based on the results we developed a micromagnetic model which includes the anisotropy as well as the coupling through the Cr spacer layer. A refined numerical analysis for the different regimes of coherent rotation of the individual layers and domain wall propagation in the hysteresis loops yield the contribution of bilinear and biquadratic coupling with respect to the Cr spacer thickness. In conclusion we found oscillation of the interlayer exchange coupling with varying coupling strength.