title: Energy minimization and ac demagnetization in a nanomagnet array.
abstract: 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.
authors.affiliation: Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: X
authors.initials: X
authors.lastname: Ke
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: C
authors.initials: C
authors.lastname: Nisoli
authors.forename: Paul E
authors.initials: PE
authors.lastname: Lammert
authors.forename: W
authors.initials: W
authors.lastname: McConville
authors.forename: R F
authors.initials: RF
authors.lastname: Wang
authors.forename: V H
authors.initials: VH
authors.lastname: Crespi
authors.forename: P
authors.initials: P
authors.lastname: Schiffer