Magnetic coupling in colloidal clusters for hierarchical self-assembly

Manipulating the way in which colloidal particles self-organise is a central principle in the design and realisation of contemporary soft matter materials. In this work we demonstrate, by using easily accessible magnetic colloids, that we can create a variety of building blocks suitable for hierarchical self-organisation. Using computer simulations, we have investigated the suitability of magnetic colloids, spherical and cubic in shape, to form small clusters with reproducible structural and magnetic properties. We find that, while the structure of these clusters is highly reproducible, their magnetic character is dependent on the shape of the constituent magnetic particles. Cubic particle shape frustrates the minimisation of the cluster energy, while spherical particles have the rotational degrees of freedom to produce equivalent magnetic configurations. Building upon these results, we validate the ability of magnetic trimers to form hierarchical assemblies, proving that the spherical magnetic particles presented here can offer a route to effectively design a viable approach for novel self-assembly processes.