Abstract
In frustrated spin systems, magnetic phase transitions underpin the formation of exotic, frustration-driven magnetic phases. Of great importance is the ability to manipulate these transitions to access specific phases, which in turn provides a means to discover and control novel phenomena. Artificial spin systems, incorporating lithographically-fabricated arrays of dipolar-coupled nanomagnets that allow real-space observation of the magnetic configurations, provide such an opportunity. In particular, the kagome spin ice is predicted to have two phase transitions, one of which is to a low temperature phase whose long-range ground state order has not been observed experimentally. To achieve this order, we change the global symmetry of the artificial kagome system, by selectively tuning the near-field nanomagnet interactions through nanoscale bridges at the vertices. By precisely tuning the interactions, we can quantify the influence of frustration on such a transition, and find that the driving force for spin and charge ordering depends on the degeneracy strength at the vertex. For the first time, we are able to observe the evolution of the magnetic configurations associated with a phase transition in real space and time.
Magnetic-charge ordering and phase transitions in monopole-conserved square spin ice
