Magnetization dynamics of weakly interacting sub-100 nm square artificial spin ices

Porro, J. M., Morley, S. A., Venero, D. A., Macêdo, R. , Rosamond, M. C., Linfield, E. H., Stamps, R. L. , Marrows, C. H. and Langridge, S. (2019) Magnetization dynamics of weakly interacting sub-100 nm square artificial spin ices. Scientific Reports, 9, 19967. (doi: 10.1038/s41598-019-56219-y) (PMID:31882867) (PMCID:PMC6934880)

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Artificial Spin Ice (ASI), consisting of a two dimensional array of nanoscale magnetic elements, provides a fascinating opportunity to observe the physics of out-of-equilibrium systems. Initial studies concentrated on the static, frozen state, whilst more recent studies have accessed the out-of-equilibrium dynamic, fluctuating state. This opens up exciting possibilities such as the observation of systems exploring their energy landscape through monopole quasiparticle creation, potentially leading to ASI magnetricity, and to directly observe unconventional phase transitions. In this work we have measured and analysed the magnetic relaxation of thermally active ASI systems by means of SQUID magnetometry. We have investigated the effect of the interaction strength on the magnetization dynamics at different temperatures in the range where the nanomagnets are thermally active. We have observed that they follow an Arrhenius-type Néel-Brown behaviour. An unexpected negative correlation of the average blocking temperature with the interaction strength is also observed, which is supported by Monte Carlo simulations. The magnetization relaxation measurements show faster relaxation for more strongly coupled nanoelements with similar dimensions. The analysis of the stretching exponents obtained from the measurements suggest 1-D chain-like magnetization dynamics. This indicates that the nature of the interactions between nanoelements lowers the dimensionality of the ASI from 2-D to 1-D. Finally, we present a way to quantify the effective interaction energy of a square ASI system, and compare it to the interaction energy computed with micromagnetic simulations.

Item Type:Articles
Additional Information:Tis work was supported by the EPSRC (grant numbers EP/L003090/1, EP/L00285X/1, and EP/L002922/1). J.M. Porro acknowledges funding from the H2020 Excellent Science-Marie Skłodowska-Curie Actions with the individual fellow No. 753025.
Glasgow Author(s) Enlighten ID:Stamps, Professor Robert and Macedo, Dr Rair
Authors: Porro, J. M., Morley, S. A., Venero, D. A., Macêdo, R., Rosamond, M. C., Linfield, E. H., Stamps, R. L., Marrows, C. H., and Langridge, 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:Scientific Reports
Publisher:Nature Research
ISSN (Online):2045-2322
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Scientific Reports 9: 19967
Publisher Policy:Reproduced under a Creative Commons License

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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