T hin-fi lm technology is widely implemented in numerous applications 1. Although fl at substrates are commonly used, we report on the advantages of using curved surfaces as a substrate. Th e curvature induces a lateral fi lm-thickness variation that allows alteration of the properties of the deposited material 2,3 . Based on this concept, a variety of implementations in materials science can be expected. As an example, a topographic pattern formed of spherical nanoparticles 4,5 is combined with magnetic multilayer fi lm deposition. Here we show that this combination leads to a new class of magnetic material with a unique combination of remarkable properties: Th e so-formed nanostructures are monodisperse, magnetically isolated, single-domain, and reveal a uniform magnetic anisotropy with an unexpected switching behaviour induced by their spherical shape. Furthermore, changing the deposition angle with respect to the particle ensemble allows tailoring of the orientation of the magnetic anisotropy, which results in tilted nanostructure material.

The deposition of Co/Pd multilayer films onto self-assembled particle arrays with particle sizes down to 50 nm leads to pronounced curvature-induced physical properties. Unlike in classical nanosystems, the so-formed single caps on top of the spherical particles exhibit a radial symmetric anisotropy orientation across their surface. Its impact on the magnetization reversal process was analyzed experimentally for different particle sizes and compared to micromagnetic simulations, offering new opportunities in the functionalization of magnetic nanostructures.

Magnetic ͓Co/ Pd͔ N multilayers grown on assemblies of spherical polystyrene particles were used as a model system for studying the influence of magnetic coupling on the magnetization reversal by changing the size of the nanoparticles as well as the total thickness of the deposited magnetic film. The coercive field and the switching field distribution are found to be strongly dependent on the size of the nanocaps and on the total thickness of the magnetic layer, indicating a strong influence of the magnetic dipole-dipole interaction on the magnetization reversal of the entire array of nanocaps. Moreover, magnetic viscosity measurements allowed the estimation of the magnetic activation volume representing the effect of thermal activation on the switching process. It was found that the magnetic activation volume is substantially smaller compared to the volume of the nanocap and almost independent of the number of bilayers, and thus the total thickness of the nanocap, supporting an inhomogeneous magnetization reversal process.

A series of [Co(x)/Pt(0.8 nm)]8 multilayers with varying individual Co layer thickness was deposited onto self-assembled particle monolayers with particle sizes as small as 58 nm forming arrays of magnetic nanostructures. A maximal out-of-plane coercivity was observed for a Co layer thickness of 0.3 nm for all particle sizes, which decreases with further increasing Co layer thickness indicating a transition of the easy axis orientation from perpendicular to the film plane at about 0.8 nm Co layer thickness. While a single-domain state is the most favorable state after perpendicular demagnetization for a Co layer thickness of up to 0.4 nm for all particle sizes, greater Co layer thicknesses reveal a multidomain state. In addition, the angle dependent magnetization reversal behavior and the domain configurations of these magnetic nanostructures were investigated systematically. At the crossover thickness of 0.4 nm Co layer thickness, a two-domain configuration can be induced for 320 nm particles by applying a magnetic field under a critical angle of 75°.

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