Perpendicular Magnetization and Generic Realization of the Ising Model   in Artificial Spin Ice
  We have studied frustrated kagome arrays and unfrustrated honeycomb arrays of magnetostatically-interacting single-domain ferromagnetic islands with magnetization normal to the plane. The measured pairwise spin correlations of both lattices can be reproduced by models based solely on nearest-neighbor correlations. The kagome array has qualitatively different magnetostatics but identical lattice topology to previously-studied 'artificial spin ice' systems composed of in-plane moments. The two systems show striking similarities in the development of moment pair correlations, demonstrating a universality in artificial spin ice behavior independent of specific realization in a particular material system. 
Sheng Zhang, Jie Li, Ian Gilbert, Jason Bartell, Michael J. Erickson,   Yu Pan, Paul E. Lammert, Cristiano Nisoli, K. K. Koh...
cond-mat.mes-hall