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Edited by Zachary Fisk, University of California, Irvine, CA, and approved August 7, 2015 (received for review February 13, 2015)
Significance
We 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.
Abstract
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 (
Footnotes
- ↵1To whom correspondence should be addressed. Email: shlee{at}virginia.edu.
Author contributions: S.-H.L. designed research; J.Y., A.S., S.D., H.U., K.I., D.P., N.P.B., Q.H., J.R.D.C., and S.-H.L. performed research; J.Y., A.S., S.D., I.K., and S.-H.L. analyzed data; and J.Y., A.S., S.D., I.K., and S.-H.L. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1503126112/-/DCSupplemental.
Freely available online through the PNAS open access option.
Spin jam state of a frustrated magnet
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