Entropy-driven order in an array of nanomagnets

Hilal Saglam; Ayhan Duzgun; Aikaterini Kargioti; Nikhil Harle; Xiaoyu Zhang; Nicholas S. Bingham; Yuyang Lao; Ian Gilbert; Joseph Sklenar; Justin D. Watts; Justin Ramberger; Daniel Bromley; Rajesh V. Chopdekar; Liam O’Brien; Chris Leighton; Cristiano Nisoli; Peter Schiffer

doi:10.1038/s41567-022-01555-6

Entropy-driven order in an array of nanomagnets

Hilal Saglam, Ayhan Duzgun, Aikaterini Kargioti, Nikhil Harle, Xiaoyu Zhang, Nicholas S. Bingham, Yuyang Lao, Ian Gilbert, Joseph Sklenar, Justin D. Watts, Justin Ramberger, Daniel Bromley, Rajesh V. Chopdekar, Liam O’Brien, Chris Leighton, Cristiano Nisoli, Peter Schiffer

Chemical Engineering and Materials Science

Research output: Contribution to journal › Article › peer-review

4 Scopus citations

Abstract

Long-range ordering is typically associated with a decrease in entropy. Yet, it can also be driven by increasing entropy in certain special cases. Here we demonstrate that artificial spin-ice arrays of single-domain nanomagnets can be designed to produce such entropy-driven order. We focus on the tetris artificial spin-ice structure, a highly frustrated array geometry with a zero-point Pauling entropy, which is formed by selectively creating regular vacancies on the canonical square ice lattice. We probe thermally active tetris artificial spin ice both experimentally and through simulations, measuring the magnetic moments of the individual nanomagnets. We find two-dimensional magnetic ordering in one subset of these moments, which we demonstrate to be induced by disorder (that is, increased entropy) in another subset of the moments. In contrast with other entropy-driven systems, the discrete degrees of freedom in tetris artificial spin ice are binary and are both designable and directly observable at the microscale, and the entropy of the system is precisely calculable in simulations. This example, in which the system’s interactions and ground-state entropy are well defined, expands the experimental landscape for the study of entropy-driven ordering.

Original language	English (US)
Pages (from-to)	706-712
Number of pages	7
Journal	Nature Physics
Volume	18
Issue number	6
DOIs	https://doi.org/10.1038/s41567-022-01555-6
State	Published - Jun 2022

Bibliographical note

Funding Information:
We thank I.-A. Chioar for fruitful discussions and A. Scholl for assistance with the early XMCD-PEEM measurements. Work at Yale University and the University of Illinois at Urbana-Champaign was funded by the US Department of Energy (DOE), Office of Basic Energy Sciences, Materials Sciences and Engineering Division under grant nos. DE-SC0010778 and DE-SC0020162 to H.S., A.K., N.H., X.Z., N.S.B., Y.L., I.G., J.S. and P.S. This research used resources of the Advanced Light Source, a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231 to R.V.C. Work at the University of Minnesota was supported by NSF through grant nos. DMR-1807124 and DMR-2103711 to J.R., J.D.W. and C.L. Work at the University of Liverpool was supported by the UK Royal Society through grant no. RGS\R2\180208 to D.B. and L.O. Work at Los Alamos National Laboratory was carried out under the auspices of the US DOE through LANL, operated by Triad National Security, LLC under contract no. 892333218NCA000001 and financed by DOE LDRD (A.D. and C.N.).

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© 2022, The Author(s), under exclusive licence to Springer Nature Limited.

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@article{e07384f6a4cf487f8062bd4c522de7bc,

title = "Entropy-driven order in an array of nanomagnets",

abstract = "Long-range ordering is typically associated with a decrease in entropy. Yet, it can also be driven by increasing entropy in certain special cases. Here we demonstrate that artificial spin-ice arrays of single-domain nanomagnets can be designed to produce such entropy-driven order. We focus on the tetris artificial spin-ice structure, a highly frustrated array geometry with a zero-point Pauling entropy, which is formed by selectively creating regular vacancies on the canonical square ice lattice. We probe thermally active tetris artificial spin ice both experimentally and through simulations, measuring the magnetic moments of the individual nanomagnets. We find two-dimensional magnetic ordering in one subset of these moments, which we demonstrate to be induced by disorder (that is, increased entropy) in another subset of the moments. In contrast with other entropy-driven systems, the discrete degrees of freedom in tetris artificial spin ice are binary and are both designable and directly observable at the microscale, and the entropy of the system is precisely calculable in simulations. This example, in which the system{\textquoteright}s interactions and ground-state entropy are well defined, expands the experimental landscape for the study of entropy-driven ordering.",

author = "Hilal Saglam and Ayhan Duzgun and Aikaterini Kargioti and Nikhil Harle and Xiaoyu Zhang and Bingham, {Nicholas S.} and Yuyang Lao and Ian Gilbert and Joseph Sklenar and Watts, {Justin D.} and Justin Ramberger and Daniel Bromley and Chopdekar, {Rajesh V.} and Liam O{\textquoteright}Brien and Chris Leighton and Cristiano Nisoli and Peter Schiffer",

note = "Funding Information: We thank I.-A. Chioar for fruitful discussions and A. Scholl for assistance with the early XMCD-PEEM measurements. Work at Yale University and the University of Illinois at Urbana-Champaign was funded by the US Department of Energy (DOE), Office of Basic Energy Sciences, Materials Sciences and Engineering Division under grant nos. DE-SC0010778 and DE-SC0020162 to H.S., A.K., N.H., X.Z., N.S.B., Y.L., I.G., J.S. and P.S. This research used resources of the Advanced Light Source, a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231 to R.V.C. Work at the University of Minnesota was supported by NSF through grant nos. DMR-1807124 and DMR-2103711 to J.R., J.D.W. and C.L. Work at the University of Liverpool was supported by the UK Royal Society through grant no. RGS\R2\180208 to D.B. and L.O. Work at Los Alamos National Laboratory was carried out under the auspices of the US DOE through LANL, operated by Triad National Security, LLC under contract no. 892333218NCA000001 and financed by DOE LDRD (A.D. and C.N.). Publisher Copyright: {\textcopyright} 2022, The Author(s), under exclusive licence to Springer Nature Limited.",

year = "2022",

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T1 - Entropy-driven order in an array of nanomagnets

AU - Saglam, Hilal

AU - Duzgun, Ayhan

AU - Kargioti, Aikaterini

AU - Harle, Nikhil

AU - Zhang, Xiaoyu

AU - Bingham, Nicholas S.

AU - Lao, Yuyang

AU - Gilbert, Ian

AU - Sklenar, Joseph

AU - Watts, Justin D.

AU - Ramberger, Justin

AU - Bromley, Daniel

AU - Chopdekar, Rajesh V.

AU - O’Brien, Liam

AU - Leighton, Chris

AU - Nisoli, Cristiano

AU - Schiffer, Peter

N1 - Funding Information: We thank I.-A. Chioar for fruitful discussions and A. Scholl for assistance with the early XMCD-PEEM measurements. Work at Yale University and the University of Illinois at Urbana-Champaign was funded by the US Department of Energy (DOE), Office of Basic Energy Sciences, Materials Sciences and Engineering Division under grant nos. DE-SC0010778 and DE-SC0020162 to H.S., A.K., N.H., X.Z., N.S.B., Y.L., I.G., J.S. and P.S. This research used resources of the Advanced Light Source, a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231 to R.V.C. Work at the University of Minnesota was supported by NSF through grant nos. DMR-1807124 and DMR-2103711 to J.R., J.D.W. and C.L. Work at the University of Liverpool was supported by the UK Royal Society through grant no. RGS\R2\180208 to D.B. and L.O. Work at Los Alamos National Laboratory was carried out under the auspices of the US DOE through LANL, operated by Triad National Security, LLC under contract no. 892333218NCA000001 and financed by DOE LDRD (A.D. and C.N.). Publisher Copyright: © 2022, The Author(s), under exclusive licence to Springer Nature Limited.

PY - 2022/6

Y1 - 2022/6

N2 - Long-range ordering is typically associated with a decrease in entropy. Yet, it can also be driven by increasing entropy in certain special cases. Here we demonstrate that artificial spin-ice arrays of single-domain nanomagnets can be designed to produce such entropy-driven order. We focus on the tetris artificial spin-ice structure, a highly frustrated array geometry with a zero-point Pauling entropy, which is formed by selectively creating regular vacancies on the canonical square ice lattice. We probe thermally active tetris artificial spin ice both experimentally and through simulations, measuring the magnetic moments of the individual nanomagnets. We find two-dimensional magnetic ordering in one subset of these moments, which we demonstrate to be induced by disorder (that is, increased entropy) in another subset of the moments. In contrast with other entropy-driven systems, the discrete degrees of freedom in tetris artificial spin ice are binary and are both designable and directly observable at the microscale, and the entropy of the system is precisely calculable in simulations. This example, in which the system’s interactions and ground-state entropy are well defined, expands the experimental landscape for the study of entropy-driven ordering.

AB - Long-range ordering is typically associated with a decrease in entropy. Yet, it can also be driven by increasing entropy in certain special cases. Here we demonstrate that artificial spin-ice arrays of single-domain nanomagnets can be designed to produce such entropy-driven order. We focus on the tetris artificial spin-ice structure, a highly frustrated array geometry with a zero-point Pauling entropy, which is formed by selectively creating regular vacancies on the canonical square ice lattice. We probe thermally active tetris artificial spin ice both experimentally and through simulations, measuring the magnetic moments of the individual nanomagnets. We find two-dimensional magnetic ordering in one subset of these moments, which we demonstrate to be induced by disorder (that is, increased entropy) in another subset of the moments. In contrast with other entropy-driven systems, the discrete degrees of freedom in tetris artificial spin ice are binary and are both designable and directly observable at the microscale, and the entropy of the system is precisely calculable in simulations. This example, in which the system’s interactions and ground-state entropy are well defined, expands the experimental landscape for the study of entropy-driven ordering.

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Entropy-driven order in an array of nanomagnets

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