Laboratoire Louis Néel (CNRS), BP166, 38042 Grenoble, France
Magnetostatic interactions between two magnetic layers through a non-magnetic spacer layer play an important role in the static and dynamic properties of spin valves and magnetic tunnel junctions. These interactions can be induced by interface roughness or edge effects, but also by a non-homogeneous orientation of the magnetization, like in magnetic domain walls. We have used time-resolved XMCD-PEEM at BESSY and high resolution static XMCD-PEEM at ELETTRA to investigate the domain wall-induced interaction between the Co and FeNi layers in magnetic tunnel junction-like FeNi/Al2O3/Co trilayers. We studied samples deposited on step-bunched Si(111) substrates with different miscut angles, giving rise to terraces with different widths. We have used the element selectivity of XMCD-PEEM to show that domain walls in the Co layer induce quasi-walls in the FeNi layer, a tilt in the local FeNi magnetization direction away from the easy axis. Domain wall charges on Co domain walls that are not parallel to the magnetization direction can moreover induce an antiferromagnetic coupling between the two magnetic layers extending over lateral distances of several microns. These domain wall-induced interactions strongly influence the fast magnetization reversal of the FeNi layer . Comparing measurements taken on different substrates shows that also the layer topography has a large influence on nucleation and domain wall dynamics.
This work was performed in collaboration with Wolfgang Kuch, Keiki Fukumoto (FU Berlin), Fabien Romanens, Salia Cherifi, Stefania Pizzini, Marlio Bonfim (LLN Grenoble), Julio Camarero (UAM Madrid), Frédéric Petroff (CNRS/Thales, Orsay), Riccardo Hertel (IFF Jülich), Andrea Locatelli and Stefan Heun (ELETTRA, Trieste).
 J. Vogel, W. Kuch, R. Hertel, K. Fukumoto, F. Romanens, M. Bonfim, S. Pizzini, F. Petroff, A. Fontaine, J. Kirschner, Phys. Rev. B 72, 020404(R) (2005).
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