Abstract
Defects can significantly affect performance of nanopatterned magnetic devices, therefore their influence on the material properties has to be understood well before the material is used in technological applications. However, this is experimentally challenging due to the inability of the control of defect characteristics in a reproducible manner. Here, we construct a micromagnetic model, which accounts for intrinsic and extrinsic defects associated with the polycrystalline nature of the material and with corrugated edges of nanostructures. The predictions of the model are corroborated by the measurements obtained for highly ordered arrays of circular Co/Pd antidots with perpendicular magnetic anisotropy. We found that magnetic properties, magnetic reversal and the evolution of the domain pattern are strongly determined by density of defects, heterogeneity of nanostructures, and edge corrugations. In particular, an increase in the Néel domain walls, as compared to Bloch walls, was observed with a increase of the antidot diameters, suggesting that a neck between two antidots can behave like a nanowire with a width determined by the array period and antidot size. Furthermore, the presence of edge corrugations can lead to the formation of a network of magnetic bubbles, which are unstable in non-patterned flat films.
Highlights
Periodic arrays of ferromagnetic nanostructures have been intensively investigated over the recent years for their fundamental and applied properties
The defects may have a strong impact on the magnetic properties[17], and their influence should be understood well before the nanopatterned material is used in technological applications
The difficulty in studying of the influence of edge defects on the magnetic reversal behavior lies in the inability to regulate their characteristics experimentally in a reproducible manner
Summary
Periodic arrays of ferromagnetic nanostructures have been intensively investigated over the recent years for their fundamental and applied properties Their importance for fundamental research stems from the low dimensionality and a large contribution of surface and edge regions resulting in magnetic properties that are not observed in bulk or continuous flat films. The possibility of tuning of the magnetic properties makes the antidot arrays a potential candidate for the microwave devices[11], magnetic sensors[12], directed transport of magnetic nanoparticles[13], and high-density storage media[14,15] In the latter case, systems with perpendicular magnetic anisotropy (PMA) are especially interesting, since they offer both a high stability and a possibility of rapid magnetic reversal[16]. The experimentally measured parameters such as coercivity or effective anisotropy are a superposition of contributions from different defects, which often cannot be studied separately[20]
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