^{1}

^{2}

^{1}

^{2}

The influence of a variation of spatial relative orientations onto the coupling dynamics and subsequent magnetic anisotropies was modeled in ferromagnetic nanowires. The wires were analyzed in the most elementary configurations, thus, arranged in pairs perpendicular to each other, leading to one-dimensional (linear) and zero-dimensional (point-like) coupling. Different distances within each elementary pair of wires and between the pairs give rise to varying interactions between parallel and perpendicular wires, respectively. Simulated coercivities show an exchange of easy and hard axes for systems with different couplings. Additionally, two of the systems exhibit a unique switching behavior which can be utilized for developing new functionalities.

Innovative magnetic storage and sensing devices, magnetic logical circuits (MLC), magnetic quantum cellular automata (MQCA), and other novel magnetic systems are based on nanoscale ferromagnetic structures [

For patterned magnetic structures [

Recent progresses in technology and measurement techniques of ferromagnetic nanowires give opportunities to analyze novel effects and applications [

Systems of four iron (Fe) wires with diameter 10 nm and length 70 nm, ordered in four different configurations (Figure

Magnetic systems composed of four nanowires, arranged in perpendicular pairs, with a different coupling within one pair/between the pairs: maximum coupling between the pairs and (a) coupling/(b) no coupling within each pair; no coupling between the pairs and (c) coupling/(d) no coupling within each pair.

The “Parallel Finite Element Micromagnetics Package (MAGPAR)” [

For meshing, finite tetrahedral elements of dimensions of maximal 3 nm were used. This value is significantly smaller than the Fe exchange length which exceeds 20 nm [

For the simulations, four different systems with the following coupling possibilities were taken into account (Figure

Simulations were carried out with the external magnetic field applied in the sample plane, for a sample orientation of 0° along the

The coercivities

Simulated coercivities of the magnetic systems depicted in Figure

For a deeper understanding of this finding, the simulated hysteresis loops are depicted in Figure

Simulated hysteresis curves for the samples depicted in Figure

Comparing Figure

A detailed study of magnetization reversal processes in fourfold nanowire systems similar to sample (b) of different dimensions has revealed the existence of six different reversal mechanisms, depending on wire length and diameter as well as on the orientation of the system to the external magnetic field (to be published). Additionally, for sample (b) even a step in the hysteresis loop can be found, which has been previously reported as a typical feature of some exchange bias systems [

In conclusion, our micromagnetic simulations of systems consisting of two perpendicular pairs of parallel wires—as an alternative to exchange and/or dipolar coupled layered systems—have shown the strong dependence of the magnetic properties on the kind of coupling between them. Additionally, some systems exhibit unexpected features which are promising for the development of new functionalities.

The authors thank the Niederrhein University of Applied Sciences for funding the project.

_{0.99}Co

_{0.01}

_{3}O

_{4}(100) elements (invited)

_{2}investigated by means of the magneto-optic Kerr effect