Photoemission electron microscopy study of remanent magnetic domain states in ferromagnetic wedge films deposited on substrates with micrometer-sized square plateaus

Abstract

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.

Magnetization reversal in cobalt antidot arrays

“…To fabricate the prepatterned substrate, the antidot pattern in the PMMA resist was first transferred using reactive ion etching ͑RIE͒ into a chromium thin film, which was subsequently used as a mask to etch holes into the silicon by RIE. 21 The latter process was developed for fabrication of antidot arrays on silicon nitride membranes required for TXM ͑the details of which we plan to publish later͒, with a thicker cobalt film to enhance the magnetic contrast. While the detailed studies presented here were mainly carried out on the 10-nm-thick films, it should be noted that for the 40-nm-thick films deposited on prepatterned substrates, there may be a small influence on the domain configuration due to stray field coupling between the continuous cobalt film with an array of holes and the corresponding cobalt dot array deposited in the lower etched regions.…”

Spin-Flop Coupling and Exchange Bias in Embedded Complex Oxide Micromagnets

“…Both unpatterned regions and 2 m  2 m square platelets were investigated. At these dimensions, the structures lie at the boundary of the expected transition from flux closure to more complicated multidomain states [29]. An all perovskite oxide structure ensures an ideal model system consisting of epitaxial layers without uncompensated spins at the AFM/FM interface.…”

Nanostructuring of GdFeCo Thin Films for Laser Induced Magnetization Switching

“…The principle of the pre-patterning method is to etch the substrate with the desired structures before the magnetic multilayer deposition is performed, such that the magnetic layer on top of the structures is at a different height and thus disconnected from the rest of the film 9,10) . First, an 80 nm thick polymethylmethacrylate (PMMA) resist is spin-coated onto a silicon substrate and patterned with an electron beam writer.…”