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.