Ground state lost but degeneracy found: the effective thermodynamics of artificial spin ice.
We analyze the rotational demagnetization of artificial spin ice, a recently realized array of nanoscale single-domain ferromagnetic islands. Demagnetization does not anneal this model system into its antiferromagnetic ground state: the moments have a static disordered configuration similar to the frozen state of the spin ice materials. We demonstrate that this athermal system has an effective extensive degeneracy and we introduce a formalism that can predict the populations of local states in this icelike system with no adjustable parameters.
Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Cristiano
C
Nisoli
Ruifang
R
Wang
Jie
J
Li
William F
WF
McConville
Paul E
PE
Lammert
Peter
P
Schiffer
Vincent H
VH
Crespi