Department of Physics, Key Laboratory of Micro-Nano Measurement-Manipulation and Physics (Ministry of Education), Beihang University, Beijing 100191, China.
International Research Institute of Multidisciplinary Science, Beihang University, Beijing 100191, China.
Sci Rep. 2017 Mar 15;7:44643. doi: 10.1038/srep44643.
In this work, a systematic study of Cu(NO)·2.5 HO (copper nitrate hemipentahydrate, CN), an alternating Heisenberg antiferromagnetic chain model material, is performed with multi-technique approach including thermal tensor network (TTN) simulations, first-principles calculations, as well as magnetization measurements. Employing a cutting-edge TTN method developed in the present work, we verify the couplings J = 5.13 K, α = 0.23(1) and Landé factors g= 2.31, g = 2.14 in CN, with which the magnetothermal properties have been fitted strikingly well. Based on first-principles calculations, we reveal explicitly the spin chain scenario in CN by displaying the calculated electron density distributions, from which the distinct superexchange paths are visualized. On top of that, we investigated the magnetocaloric effect (MCE) in CN by calculating its isentropes and magnetic Grüneisen parameter. Prominent quantum criticality-enhanced MCE was uncovered near both critical fields of intermediate strengths as 2.87 and 4.08 T, respectively. We propose that CN is potentially a very promising quantum critical coolant.
在这项工作中，我们采用了包括热张量网络（TTN）模拟、第一性原理计算和磁化测量在内的多种技术手段，对交替的海森堡反铁磁链模型材料 Cu(NO)·2.5 HO（硝酸铜半水合物，CN）进行了系统研究。利用本工作中开发的先进 TTN 方法，我们验证了 CN 中的耦合 J = 5.13 K、α = 0.23(1) 和 Landé 因子 g= 2.31、g = 2.14，用这些参数可以很好地拟合磁热性质。基于第一性原理计算，我们通过显示计算得到的电子密度分布，明确揭示了 CN 中的自旋链情景，从中可以直观地看到明显的超交换路径。此外，我们通过计算等熵和磁 Grüneisen 参数研究了 CN 的磁热效应（MCE）。在分别为 2.87 和 4.08 T 的两个中等强度临界场附近，发现了显著的量子临界点增强的 MCE。我们提出，CN 可能是一种很有前途的量子临界冷却剂。
