Absence of Pauling's residual entropy in thermally equilibrated Dy2Ti2O7
Absence of Pauling's residual entropy in thermally equilibrated Dy2Ti2O7
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DOI：
10.1038/nphys2591
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发表时间：
2013-06-01
期刊：
影响因子：
19.6
通讯作者：
Kycia, J. B.
中科院分区：
文献类型：
--
作者：
Pomaranski, D.;Yaraskavitch, L. R.;Kycia, J. B.
在Dy2Ti2O7中发现自旋-冰相是十多年来磁性材料中最重要的发现之一(1-3)。自旋冰后来与磁单极子的表现联系在一起(4，5)，甚至可能有助于我们对浮现量子电动力学的理解(6)。自旋-冰模型基于鲍林在水冰中的几何受挫模型的完美类比，并预测了相同的剩余熵，这一预测得到了大量测量(1，2，7-11)的证实。在这里，我们给出了Dy2Ti2O7的比热的结果，说明了为什么以前的测量无法正确地捕捉到它的低温行为。通过仔细跟踪流入和流出材料的热量，我们观察到了以前没有检测到的不消失的比热。这一行为在两个Dy2Ti2O7样品中得到了证实，其中低于0.6K的冷却揭示了与Pauling剩余熵的偏差，这对自旋冰的真实磁性基态提出了质疑。
The discovery of the spin-ice phase in Dy2Ti2O7 numbers among the most significant findings in magnetic materials in over a decade(1-3). Spin ice has since been associated with the manifestation of magnetic monopoles(4,5) and may even inform our understanding of emergent quantum electrodynamics(6). The spin-ice model is based on an elegant analogy to Pauling's model of geometrical frustration in water ice, and predicts the same residual entropy, as confirmed by numerous measurements(1,2,7-11). Here we present results for the specific heat of Dy2Ti2O7, demonstrating why previous measurements were unable to correctly capture its low-temperature behaviour. By carefully tracking the flow of heat into and out of the material, we observe a non-vanishing specific heat that has not previously been detected. This behaviour is confirmed in two samples of Dy2Ti2O7, in which cooling below 0.6 K reveals a deviation from Pauling's residual entropy, calling into question the true magnetic ground state of spin ice.