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标题：Supercooled spin liquid state in the frustrated pyrochlore Dy2Ti2O7
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作者：Ethan R. Kassner ; Azar B. Eyvazov ; Benjamin Pichler 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：28
页码：8549-8554
DOI：10.1073/pnas.1511006112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceFrustrated magnetic pyrochlore systems, in which there are many possible favored spin configurations, may host a variety of exotic magnetic phases. For example, some models predict that Dy2Ti2O7 hosts a fluid of mobile magnetic "monopoles" that interact via a magnetic Coulomb interaction. Here, we introduce a novel measurement technique that realizes periodic boundary conditions, and use it to examine the magnetization transport dynamics of tori of Dy2Ti2O7. We identify multiple phenomena in the dynamics of Dy2Ti2O7 that are characteristic of a supercooled magnetic liquid approaching a glass transition. This highly unusual classical spin liquid forms in a structurally ordered crystal and therefore it may constitute the approach to a novel magnetic glass state. A "supercooled" liquid develops when a fluid does not crystallize upon cooling below its ordering temperature. Instead, the microscopic relaxation times diverge so rapidly that, upon further cooling, equilibration eventually becomes impossible and glass formation occurs. Classic supercooled liquids exhibit specific identifiers including microscopic relaxation times diverging on a Vogel-Tammann-Fulcher (VTF) trajectory, a Havriliak-Negami (HN) form for the dielectric function [IMG]f1.gif" ALT="Formula" BORDER="0">, and a general Kohlrausch-Williams-Watts (KWW) form for time-domain relaxation. Recently, the pyrochlore Dy2Ti2O7 has become of interest because its frustrated magnetic interactions may, in theory, lead to highly exotic magnetic fluids. However, its true magnetic state at low temperatures has proven very difficult to identify unambiguously. Here, we introduce high-precision, boundary-free magnetization transport techniques based upon toroidal geometries and gain an improved understanding of the time- and frequency-dependent magnetization dynamics of Dy2Ti2O7. We demonstrate a virtually universal HN form for the magnetic susceptibility [IMG]f2.gif" ALT="Formula" BORDER="0"> a general KWW form for the real-time magnetic relaxation, and a divergence of the microscopic magnetic relaxation rates with the VTF trajectory. Low-temperature Dy2Ti2O7 therefore exhibits the characteristics of a supercooled magnetic liquid. One implication is that this translationally invariant lattice of strongly correlated spins may be evolving toward an unprecedented magnetic glass state, perhaps due to many-body localization of spin.
关键词：spin liquid ; supercooled liquids ; magnetic dynamics ; periodic boundaries