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M. Huth, L. Keller, A. Mohanad, J. Pieper, C. Gspan, I. Stockem, C. Schröder, S. Barth, R. Winkler, H. Plank, M. Pohlit, J. Müller:
"Complex 3D magnetic nanostructures prepared by FEBID";
Talk: CELINA 2017 The fourth meeting of COST Action CM1301, Porto; 2017-09-13 - 2017-09-16.

Building nanotechnological analogues of naturally occurring magnetic structures has proven to be an extremely powerful approach to studying topics like geometry-induced magnetic frustration and to provide model systems for statistical physics. Moreover, it practically allows to engineer novel physical properties by realizing artificial lattice geometries that are not accessible via natural crystallization or chemical synthesis. This has been accomplished with great success in the field of two-dimensional (2D) artificial spin ice systems over the last decade with important branches also reaching into the field of novel magnetic logic devices, such as, magnetic quantum cellular automata. Although first proposals have been made to advance into three-dimensions (3D), established nanofabrication pathways based on sophisticated electron beam lithography have not been adapted to obtain free-form 3D nanostructures. Here we demonstrate the direct-write fabrication of freestanding, ferromagnetic 3D nano-architectures, which does, amongst other things, allow for full control over the degree of magnetic frustration. In particular, we have realized free-form shapes featuring three- and four-edge magnetic vertex types as important building blocks for more complex, geometrically frustrated 3D vertex configurations. By employing micro-Hall sensing based on a two-dimensional electron gas, we have determined the magnetic stray field generated by our free-form structures in an externally applied magnetic field. Taking information from microstructure analysis into account, we have performed micromagnetic and macro-spin simulations that allow us to deduce the spatial magnetization profiles in the structures and analyze their switching behavior based on the singledomain magnetic element paradigm followed in 2D artificial spin ice structures. In geometrically frustrated systems, the occurring magnetic configurations as well as the transitions between them are controlled by both, the topology and geometry of the interacting magnetic elements. Our approach allows for the fabrication and magnetic characterization of arrays of free-form 3D structures. Furthermore, the 3D elements made of magnetic material can be combined with other 3D elements of different chemical composition and intrinsic material properties, such as superconducting, plasmonactive, or dielectric materials. We therefore expect that the direct-write approach presented here will inspire innovative free-form design-oriented ideas to engineer nanoscale systems with new emergent physics.

http://publik.tuwien.ac.at/files/publik_263817.pdf