Field Controlled Magnetisation Patterns in Three-Arm Star Shaped Nanoparticles as Prototypes of Reconfigurable Routing and Vortex State Memory Devices

A model of nanoparticles has been designed to resemble partly self-similar ferroelastic star-like domain textures. Numerical computations have been used to find the equilibrium configurations of magnetisation in such systems. As expected from symmetry, the self-similar initial states give room to other types of domain structure as a function of the star parameters. When relaxed without external field the self-similar pattern mostly turns to a massive vortex in the center with radially oriented domains in the peripheral arms of the star. In contrast to that a random initial state ends up in a configuration of a triple valve with one input and two outputs or vice versa in analogy to logical gates. A treatment with an in-plane magnetic field always leads to the valve configuration. The triple-valve states turn out stable and the vortex ones metastable. The results may be useful in the design of magnetic based logic devices.