Energy minimization and AC demagnetization in a nanomagnet array
  We study AC demagnetization in frustrated arrays of single-domain ferromagnetic islands, exhaustively resolving every (Ising-like) magnetic degree of freedom in the systems. Although the net moment of the arrays is brought near zero by a protocol with sufficiently small step size, the final magnetostatic energy of the demagnetized array continues to decrease for finer-stepped protocols and does not extrapolate to the ground state energy. The resulting complex disordered magnetic state can be described by a maximum-entropy ensemble constrained to satisfy just nearest-neighbor correlations. 
X. Ke, J. Li, C. Nisoli, Paul E. Lammert, W. McConville, R. F. Wang,   V. H. Crespi, and P. Schiffer