We have carried out a detailed study of the magnetic switching in square lattice cobalt antidot arrays with periods ranging from 2 m down to 200 nm ͑antidot size= antidot separation͒. Magneto-optical Kerr effect measurements show first a small change in the magnetization due to a reversible rotation of the magnetic spins in the antidot rows, followed by a large change due to reversal of the antidot array columns parallel to the applied field. Employing x-ray photoemission electron microscopy and transmission x-ray microscopy, the latter irreversible process was observed as a nucleation and propagation of discrete domain chains. The propagating chain ends are blocked by perpendicular chains present in the antidot rows via various mechanisms revealed by micromagnetic simulations.

Photoemission electron microscopy has been used to determine the orientation of individual antiferromagnetic domains in LaFeO 3 thin films. We found the antiferromagnetic axes are tilted by 20°out of the surface plane and have a different sign of the x-ray magnetic linear dichroism compared to previous reports on LaFeO 3. Using multiplet calculations, we show that this sign depends on the orientation of the magnetization with respect to the crystalline axes. This has important bearings on the correct analysis of the coupling between ferromagnetic and antiferromagnetic films in exchange bias systems.

We present a detailed study of the remanent magnetic domain configurations in demagnetized polycrystalline ferromagnetic thin film wedges of cobalt and Permalloy deposited on prepatterned silicon substrates with micrometer-sized square plateaus, which have a height of 125 nm, using photoemission electron microscopy. We have observed the continuous evolution of the magnetic domain states in the square ferromagnetic elements on top of the plateaus as a function of film thickness. At high film thickness we observe the Landau state, which is the expected lowest energy state, but at lower thickness we see a variety of metastable states which are trapped as a result of local pinning. In a small thickness range below 10 nm, the square elements contain 360°walls and small domains which are likely to be a result of local effects such as magnetocrystalline anisotropy and edge roughness. We are able to simultaneously observe the development of the magnetic domains in the continuous polycrystalline film surrounding the plateaus and, rather than the expected large domains, we observe at intermediate film thickness a significant modification of the domain configuration to small domains. Here the roughness of the silicon substrate surrounding the plateaus, which is due to the reactive ion etching process used to prepare the prepatterned substrates, gives rise to local stray fields in the ferromagnetic film which play an important role in determining the resulting domain structure.

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Photoemission electron microscopy was employed to study the antiferromagnetic domain structure in patterned LaFeO3 thin films. No influence of the patterning was observed and, using forward scattered electron scanning electron microscopy, a one-to-one correlation of the crystallographic domain structure with the antiferromagnetic domains was found. We deduce that the antiferromagnetic domain structure of thin LaFeO3 films is determined by the crystallographic domains and this explains why it is not influenced by patterning. Determining the origin of antiferromagnetic domains provides an important step in the understanding of patterned exchange bias systems where antiferromagnetic films play a primary role.