Artificial spin ice [1] is a useful model system because its component magnetic dots are large enough that their configuration states can be imaged directly. On the other hand, this large size means that dynamics must be driven by an external field, which acts uniformly on all macrospins. These global dynamics are highly constrained and many states are inaccessible, regardless of their energy. 



In this talk, I will discuss how dynamics can be modelled in an ideal system via equations describing the evolution of vertex populations. [2] I will then show how quenched disorder, which is present in any real system, dramatically changes dynamics, in a way that can be interpreted using an exact enumeration of the system's configurational phase space. This provides an elegant means to study disorder effects in a systematic and quantitative way. [3]



[1] R. F. Wang et al., Artificial ‘spin ice' in a geometrically frustrated lattice of nanoscale ferromagnetic islands. Nature 439, 303 (2006).

[2] Zoe Budrikis, Paolo Politi and R. L. Stamps, Vertex dynamics in finite two-dimensional square spin ices. Phys. Rev. Lett. 105, 017201 (2010).

[3] Zoe Budrikis, Paolo Politi and R. L. Stamps, Diversity enabling equilibration: disorder and the ground state in artificial spin ice. arXiv:1108.0536.