Ice-rule made manifold: phase transitions, topological defects and manifold restoration in two-dimensional artificial spin systems

Macauley, G. M. , Paterson, G. W. , Li, Y., Macêdo, R. , McVitie, S. and Stamps, R. L. (2019) Ice-rule made manifold: phase transitions, topological defects and manifold restoration in two-dimensional artificial spin systems. arXiv, (Unpublished)

Abstract

Artificial spin ices are arrays of correlated nano-scale magnetic islands that prove an excellent playground in which to study the role of topology in critical phenomena. Here, we investigate a continuum of spin ice geometries, parameterised by rotation of the islands. In doing so, we morph from the classic square ice to the recently studied pinwheel geometry, with the rotation angle acting as a proxy for controlling inter-island interactions. We experimentally observe a change in ground state magnetic order from antiferromagnetic to ferromagnetic across this class of geometries using Lorentz transmission electron microscopy on thermally annealed cobalt arrays. The change in ordering leads to an apparent change in the nature of the defects supported: from one-dimensional strings in the antiferromagnetic phase to two-dimensional vortex-like structures in the ferromagnetic one, consistent with the scaling predicted by the Kibble-Zurek mechanism. Our results show how magnetic order in artificial spin i ces can be tuned by changes in geometry so that a truly frustrated ice-rule phase is possible in two-dimensional systems. Furthermore, we demonstrate this system as a testbed to investigate out-of-equilibrium dynamics across phases.

• Item Type: Articles
• Status: Unpublished
• Refereed: No
• Glasgow Author(s) Enlighten ID: McVitie, Professor Stephen and Stamps, Professor Robert and Macauley, Mr Gavin and Paterson, Dr Gary and Li, Miss Yue and Macedo, Dr Rair
• Authors: Macauley, G. M., Paterson, G. W., Li, Y., Macêdo, R., McVitie, S., and Stamps, R. L.
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering; College of Science and Engineering > School of Physics and Astronomy
• Journal Name: arXiv
• Copyright Holders: Copyright © 2019 The Authors
• Publisher Policy: Reproduced with the permission of the Author