Schmidt M, Zimmer F M, Magalhaes S G
Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil.
J Phys Condens Matter. 2017 Apr 26;29(16):165801. doi: 10.1088/1361-648X/aa6060. Epub 2017 Mar 16.
The interplay between geometric frustration (GF) and bond disorder is studied in the Ising kagome lattice within a cluster approach. The model considers antiferromagnetic short-range couplings and long-range intercluster disordered interactions. The replica formalism is used to obtain an effective single cluster model from where the thermodynamics is analyzed by exact diagonalization. We found that the presence of GF can introduce cluster freezing at very low levels of disorder. The system exhibits an entropy plateau followed by a large entropy drop close to the freezing temperature. In this scenario, a spin-liquid (SL) behavior prevents conventional long-range order, but an infinitesimal disorder picks out uncompensated cluster states from the multi-degenerate SL regime, potentializing the intercluster-disordered coupling and bringing the cluster spin-glass state. To summarize, our results suggest that the SL state combined with low levels of disorder can activate small clusters, providing hypersensitivity to the freezing process in geometrically frustrated materials and playing a key role in the glassy stabilization. We propose that this physical mechanism could be present in several geometrically frustrated materials. In particular, we discuss our results in connection with the recent experimental investigations of the Ising kagome compound CoMg(OH)Cl.
在团簇近似下，研究了伊辛戈薇晶格中几何阻挫（GF）与键无序之间的相互作用。该模型考虑反铁磁短程耦合和长程团簇间无序相互作用。利用复制形式从有效单团簇模型中通过精确对角化分析热力学。我们发现，GF的存在可在非常低的无序水平下引入团簇冻结。系统在接近冻结温度时呈现出一个熵平台，随后是大幅的熵降。在这种情况下，自旋液体（SL）行为阻止了传统的长程序，但极小的无序从多重简并的SL区域中挑选出未补偿的团簇态，增强了团簇间无序耦合并导致团簇自旋玻璃态。总之，我们的结果表明，SL态与低水平的无序相结合可激活小团簇，使几何阻挫材料对冻结过程具有超敏感性，并在玻璃态稳定中起关键作用。我们提出这种物理机制可能存在于几种几何阻挫材料中。特别是，我们结合伊辛戈薇化合物CoMg(OH)Cl的近期实验研究讨论了我们的结果。
