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Realization of ground state in artificial kagome spin ice via topological defect-driven magnetic writing

Abstract

Arrays of non-interacting nanomagnets are widespread in data storage and processing. As current technologies approach fundamental limits on size and thermal stability, enhancing functionality through embracing the strong interactions present at high array densities becomes attractive. In this respect, artificial spin ices are geometrically frustrated magnetic metamaterials that offer vast untapped potential due to their unique microstate landscapes, with intriguing prospects in applications from reconfigurable logic to magnonic devices or hardware neural networks. However, progress in such systems is impeded by the inability to access more than a fraction of the total microstate space. Here, we demonstrate that topological defect-driven magnetic writing—a scanning probe technique—provides access to all of the possible microstates in artificial spin ices and related arrays of nanomagnets. We create previously elusive configurations such as the spin-crystal ground state of artificial kagome dipolar spin ices and high-energy, low-entropy ‘monopole-chain’ states that exhibit negative effective temperatures.

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Fig. 1: The TMW process.
Fig. 2: Realization of TMW read/write functionality in ASI.
Fig. 3: Realization of the kagome ASI ground state via TMW.
Fig. 4: Negative effective temperature in ASI.

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Acknowledgements

This work was supported by the Engineering and Physical Sciences Research Council (grant number EP/G004765/1) and the Leverhulme Trust (grant number RPG 2012-692) to W.R.B. and supported by the Engineering and Physical Sciences Research Council (grant number EP/J014699/1) to L.F.C.

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J.C.G. conceived the experiment with the assistance of D.M.A., D.M.B. and W.R.B. J.C.G. fabricated the samples and performed the experimental measurements, J.C.G., V.L.B. and A.M. developed the practical selective writing capabilities on SPM systems. J.C.G., D.M.A. and D.M.B. performed micromagnetic simulations. J.C.G. performed the experimental measurements and D.M.A. performed the effective temperature analysis. J.C.G., D.M.A., W.R.B. and L.F.C. contributed to the manuscript. All authors contributed to discussions informing the research.

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Correspondence to Jack C. Gartside.

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Gartside, J.C., Arroo, D.M., Burn, D.M. et al. Realization of ground state in artificial kagome spin ice via topological defect-driven magnetic writing. Nature Nanotech 13, 53–58 (2018). https://doi.org/10.1038/s41565-017-0002-1

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