Temperature driven macro-ferromagnetism in 'pinwheel' artificial spin ice

Artificial spin ice are patterned structure of arranged magnetic elements such that their interactions produce correlations and competitions that can be used to generate non-trivial dynamics and complex magnetic orderings. In this work, we investigate thermodynamic properties of geometries which are simple but fundamental variants of the original square lattice. We shown how a simple rotation of the elements induces a drastic change in the dipolar energy.

We have used Monte Carlo simulations to understand thermal induced ordering processes in artificial spin ice and a curious emergent chiral symmetry breaking that appears in the new spin ice structures (specially at 45⁰). This new system has also shown to be a model for studying a classical counterpart to a quantum phase transition. Here we show how the classic antiferromagnetic spin ice array (0⁰) becomes ferromagnetic (45⁰) and by doing so flux closure vortex-like magnetisation patter emerge due to boundary effects (note that such structure is not seen when periodic boundary conditions (PBC) are considered).