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：37
页码：11519-11523
DOI：10.1073/pnas.1503126112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceWe report experimental evidence for a glassy state induced by quantum fluctuations, a spin jam, that is realized in SrCr9pGa12-9pO19 [SCGO(p)], a highly frustrated magnet, in which the magnetic Cr3+ (s = 3/2) ions form a quasi-two-dimensional triangular system of bipyramids. Our new experimental data and our theoretical spin jam model provide, for the first time, to our knowledge, a coherent understanding of the existing experimental data of this fascinating system. Furthermore, our findings strongly support the possible existence of purely topological glassy states. Since the discovery of spin glasses in dilute magnetic systems, their study has been largely focused on understanding randomness and defects as the driving mechanism. The same paradigm has also been applied to explain glassy states found in dense frustrated systems. Recently, however, it has been theoretically suggested that different mechanisms, such as quantum fluctuations and topological features, may induce glassy states in defect-free spin systems, far from the conventional dilute limit. Here we report experimental evidence for existence of a glassy state, which we call a spin jam, in the vicinity of the clean limit of a frustrated magnet, which is insensitive to a low concentration of defects. We have studied the effect of impurities on SrCr9pGa12-9pO19 [SCGO(p)], a highly frustrated magnet, in which the magnetic Cr3+ (s = 3/2) ions form a quasi-2D triangular system of bipyramids. Our experimental data show that as the nonmagnetic Ga3+ impurity concentration is changed, there are two distinct phases of glassiness: an exotic glassy state, which we call a spin jam, for the high magnetic concentration region ([IMG]f1.gif" ALT="Formula" BORDER="0">) and a cluster spin glass for lower magnetic concentration ([IMG]f2.gif" ALT="Formula" BORDER="0">). This observation indicates that a spin jam is a unique vantage point from which the class of glassy states of dense frustrated magnets can be understood.
