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.
Nisoli
Cristiano
C
Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Wang
Ruifang
R
Li
Jie
J
McConville
William F
WF
Lammert
Paul E
PE
Schiffer
Peter
P
Crespi
Vincent H
VH