Heisenberg pseudo-exchange and emergent anisotropies in field-driven pinwheel artificial spin ice

Paterson, G. W. et al. (2019) Heisenberg pseudo-exchange and emergent anisotropies in field-driven pinwheel artificial spin ice. Physical Review B, 100(17), 174410. (doi: 10.1103/PhysRevB.100.174410)

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Rotating all islands in square artificial spin ice (ASI) uniformly about their centres gives rise to the recently reported pinwheel ASI. At angles around 45o, the antiferromagnetic ordering changes to ferromagnetic and the magnetic configurations of the system exhibit near-degeneracy, making it particularly sensitive to small perturbations. We investigate through micromagnetic modelling the influence of dipolar fields produced by physically extended islands in field-driven magnetisation processes in pinwheel arrays, and compare the results to hysteresis experiments performed using Lorentz transmission electron microscopy. We find that magnetisation end-states induce a Heisenberg pseudo-exchange interaction that governs both the inter-island coupling and the resultant array reversal process. Symmetry reduction gives rise to anisotropies and array-corner mediated avalanche reversals through a cascade of nearest-neighbour (NN) islands. The symmetries of the anisotropy axes are related to those of the geometrical array but are misaligned to the array axes as a result of the correlated interactions between neighbouring islands. The NN dipolar coupling is reduced by decreasing the island size and, using this property, we track the transition from the strongly coupled regime towards the pure point dipole one and observe modification of the ferromagnetic array reversal process. Our results shed light on important aspects of the interactions in pinwheel ASI, and demonstrate a mechanism by which their properties may be tuned for use in a range of fundamental research and spintronic applications.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Macauley, Mr Gavin and Paterson, Dr Gary and Ferguson, Mr Ciaran and Li, Miss Yue and McVitie, Professor Stephen and Stamps, Professor Robert and Macedo, Dr Rair
Authors: Paterson, G. W., Macauley, G. M., Li, Y., Macêdo, R., Ferguson, C., Morley, S. A., Rosamond, M. C., Linfield, E. H., Marrows, C. H., Stamps, R. L., and McVitie, S.
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:Physical Review B
Publisher:American Physical Society
ISSN (Online):1550-235X
Published Online:07 November 2019
Copyright Holders:Copyright © 2019 American Physical Society
First Published:First published in Physical Review B 100(17): 174410
Publisher Policy:Reproduced in accordance with the publisher copyright policy
Related URLs:
Data DOI:10.5525/gla.researchdata.900

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
168906Artificial spin ice: designer matter far from equilibriumStephen McVitieEngineering and Physical Sciences Research Council (EPSRC)EP/L002922/1P&S - Physics & Astronomy
190883Consortium for advanced materials based on spin chiralityStephen McVitieEngineering and Physical Sciences Research Council (EPSRC)EP/M024423/1P&S - Physics & Astronomy