Speakers
Description
The configuration of domains in ferromagnetic materials is determined by the interplay of competing energy terms. In ordered systems with zero net magnetisation, however, it is much less understood how microscopic coupling mechanisms affect the size and morphology of domains and domain walls. In order to access all relevant magnetic degrees of freedom, we investigate the formation of domains in a ferroic model system consisting of planar dipolar-coupled Ising-like ferromagnetic building blocks. These nanomagnets are arranged on a square lattice such that a unit cell yields a vortex-like compensated magnetisation and the as-grown state consists of domains with uniform magnetic handedness. By varying the distances between nanomagnets, we can independently tune the interaction strengths for the inter- and intra-vortex coupling. Using magnetic force microscopy and Monte-Carlo simulations, we examine a general phase diagram and link the average domain size to the ratio of inter- and intra-vortex coupling strength. We observe ratio-dependent transitions to short-range order above the critical temperature that determine the resulting substructure of a domain wall. We further demonstrate how to switch the orientation of the emergent order parameter by the application of an effective conjugate field using a magnetic-tip-assisted poling technique. Our work reveals an approach to model, tailor and manipulate ferroic order and provides insight into the formation of domains in materials with zero net magnetisation.
