Magnetic multilayers on nanospheres

Abstract

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.

Engineering Curvature-Induced Anisotropy in Thin Ferromagnetic Films

“…A possible experimental confirmation of our findings is corroborated by recent efforts to engineer anisotropy in thin films by substrate curvature, following pioneering work [14] and, in particular, Ref. [15], where the PMA has been obtained by depositing in-plane anisotropy Fe-Gd alloys on a nanosphere array.…”

“…In particular, in multilayers consisting of alternating ferromagnetic and heavy-metal (such as Pt) layers, PMA has been attributed to strong spin-orbit interaction at the interfaces [8][9][10][11][12][13]. However, in thin magnetic films, PMA may exist [14,15] without an additional heavy-metal layer, which enhances spin-orbit interaction in the system, thus pointing to a more general perpendicular anisotropy mechanism.…”

Dynamic states of cells adhering in shear flow: From slipping to rolling

“…Experimentally it is certainly a challenge to obtain similar data in flow chamber experiments for micron-sized beads or cells. In principle, making use of recent nanotechnological developments one could attach receptors to micron-sized beads which are covered with anisotropic surface layers [60,61]. If these layers are anisotropically reflective, rotational motion of the spheres can be recorded.…”

Magnetoresistive effects in Co/Pd multilayers on self-assembled nanoparticles (invited)

“…10 In this regard, another innovative approach to create nanostructure arrays is the deposition of Co/Pt and Co/Pd multilayers onto monolayers of selfassembled nanoparticles. [13][14][15] The system provides unique curvature-induced magnetic properties combined with the advantages of patterning magnetic structures by means of self-assembly over large areas. The effective anisotropy of Co/Pd multilayers in general can be tailored by adjusting the deposition parameters and individual layer thicknesses.…”

“…Apart from the orientation of the anisotropy axis, its strength varies according to the layer thickness. 13 The thickness of the deposited layers decreases from the top of each particle towards the sides. If the thickness of the Co layers falls below one monolayer, the system forms a dilute Co-Pd alloy.…”