Collective magnetism in an artificial 2D XY spin system.
Collective magnetism in an artificial 2D XY spin system.
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DOI：
10.1038/s41467-018-05216-2
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发表时间：
2018-07-20
影响因子：
16.6
通讯作者：
Heyderman LJ
中科院分区：
文献类型：
--
作者：
Leo N;Holenstein S;Schildknecht D;Sendetskyi O;Luetkens H;Derlet PM;Scagnoli V;Lançon D;Mardegan JRL;Prokscha T;Suter A;Salman Z;Lee S;Heyderman LJ
由于波动和相关性之间的强烈竞争，具有连续自旋自由度的二维磁系统表现出丰富的热行为谱。当此类系统通过各向异性偶极相互作用结合耦合时，就会出现离散对称性，这种对称性可以自发破坏，从而形成低温有序相。然而，在晶体材料中实验实现这种二维自旋系统很困难，因为偶极耦合通常比交换相互作用弱得多。在这里，我们实现了二维静磁耦合 XY 自旋系统，其中纳米级热活性磁盘放置在方形晶格上。利用低能μ子自旋弛豫和软X射线散射，我们观察到了临界温度下的相关动力学以及低温下静态长程有序的出现，这与偶极耦合XY自旋系统的理论预测相一致。此外，通过修改样品设计，我们证明了在具有连续自由度的热活性人工自旋系统中调整集体磁行为的可能性。磁性超材料可以设计为提供受挫系统模型，从而可以通过实验测试理论预测。在这里，作者实现了具有偶极相互作用的 2D XY 模型，并发现了与低温有序态预测一致的行为。
Two-dimensional magnetic systems with continuous spin degrees of freedom exhibit a rich spectrum of thermal behaviour due to the strong competition between fluctuations and correlations. When such systems incorporate coupling via the anisotropic dipolar interaction, a discrete symmetry emerges, which can be spontaneously broken leading to a low-temperature ordered phase. However, the experimental realisation of such two-dimensional spin systems in crystalline materials is difficult since the dipolar coupling is usually much weaker than the exchange interaction. Here we realise two-dimensional magnetostatically coupled XY spin systems with nanoscale thermally active magnetic discs placed on square lattices. Using low-energy muon-spin relaxation and soft X-ray scattering, we observe correlated dynamics at the critical temperature and the emergence of static long-range order at low temperatures, which is compatible with theoretical predictions for dipolar-coupled XY spin systems. Furthermore, by modifying the sample design, we demonstrate the possibility to tune the collective magnetic behaviour in thermally active artificial spin systems with continuous degrees of freedom. Magnetic metamaterials can be designed to provide models of frustrated systems that allow theoretical predictions to be experimentally tested. Here the authors realise a 2D XY model with dipolar interactions and find behaviour consistent with predictions of a low-temperature ordered state.
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影响因子：
4
作者：
Arnalds, Unnar B.;Ahlberg, Martina;Hjorvarsson, Bjorgvin
通讯作者：
Hjorvarsson, Bjorgvin
影响因子：
8.6
作者：
Ewerlin, Melanie;Demirbas, Derya;Zabel, Hartmut
通讯作者：
Zabel, Hartmut
影响因子：
19.6
作者：
Farhan, A.;Derlet, P. M.;Heyderman, L. J.
通讯作者：
Heyderman, L. J.
影响因子：
3.7
作者：
Ha, JK;Hertel, R;Kirschner, J
通讯作者：
Kirschner, J
DOI：
10.1088/0022-3719/6/7/010
发表时间：
1973-01-01
期刊：
JOURNAL OF PHYSICS C-SOLID STATE PHYSICS
影响因子：
--
作者：
Kosterlitz, JM;Thouless, DJ
通讯作者：
Thouless, DJ