TY - JOUR
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 - 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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U2 - 10.1038/s41567-022-01555-6
DO - 10.1038/s41567-022-01555-6
M3 - Article
AN - SCOPUS:85127624802
SN - 1745-2473
VL - 18
SP - 706
EP - 712
JO - Nature Physics
JF - Nature Physics
IS - 6
ER -