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Title: Disordered artificial spin ices: Avalanches and criticality (invited)

We show that square and kagome artificial spin ices with disconnected islands exhibit disorder-induced nonequilibrium phase transitions. The critical point of the transition is characterized by a diverging length scale and the effective spin reconfiguration avalanche sizes are power-law distributed. For weak disorder, the magnetization reversal is dominated by system-spanning avalanche events characteristic of a supercritical regime, while at strong disorder, the avalanche distributions have subcritical behavior and are cut off above a length scale that decreases with increasing disorder. The different type of geometrical frustration in the two lattices produces distinct forms of critical avalanche behavior. Avalanches in the square ice consist of the propagation of locally stable domain walls separating the two polarized ground states, and we find a scaling collapse consistent with an interface depinning mechanism. In the fully frustrated kagome ice, however, the avalanches branch strongly in a manner reminiscent of directed percolation. We also observe an interesting crossover in the power-law scaling of the kagome ice avalanches at low disorder. Our results show that artificial spin ices are ideal systems in which to study a variety of nonequilibrium critical point phenomena as the microscopic degrees of freedom can be accessed directly in experiments.
Authors:
; ;  [1] ;  [2]
  1. Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  2. Faculty of Mathematics and Computer Science, Babes-Bolyai University, RO-400591 Cluj-Napoca (Romania)
Publication Date:
OSTI Identifier:
22402971
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 17; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DEGREES OF FREEDOM; DOMAIN STRUCTURE; GROUND STATES; INTERFACES; MAGNETIC FIELD REVERSAL; MAGNETIZATION; PHASE TRANSFORMATIONS; SPIN