Finite temperature properties and frustrated ferromagnetism in a square lattice Heisenberg model
Finite temperature properties and frustrated ferromagnetism in a square lattice Heisenberg model
复制标题
方晶格海森堡模型中的有限温度特性和受挫铁磁性
DOI：
10.1140/epjb/e2004-00156-3
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
P. Thalmeier
中科院分区：
文献类型：
--
作者：
N. Shannon;B. Schmidt;K. Penc;P. Thalmeier
摘要：具有反铁磁最近邻和次近邻相互作用的方晶格上的自旋 1/2 海森堡模型（J1-J2 模型）长期以来一直作为二维受挫量子磁体的范例进行研究。然而，直到最近，此类系统的第一个实验实现才被合成。最新材料 Pb2VO(PO4)2 似乎具有混合的铁磁和反铁磁交换耦合。有鉴于此，我们将 J1-J2 模型的半经典处理扩展到包括铁磁相互作用，并基于 8、16 和 20 个位点簇的精确对角化对模型的有限温度特性进行分析。我们提出，可以使用扩散中子散射来解决仅从热力学性质确定 J1 和 J2 的比率和符号所固有的模糊性，并使用有限温度 Lanczos 算法对相关的高温自旋-自旋相关函数进行预测。还简要讨论了铁磁 J1 发生自旋液相的可能性。
Abstract.The spin 1/2 Heisenberg model on a square lattice with antiferromagnetic nearest- and next-nearest neighbour interactions (the J1-J2 model) has long been studied as a paradigm of a two-dimensional frustrated quantum magnet. Only very recently, however, have the first experimental realisations of such systems been synthesized. The newest material, Pb2VO(PO4)2 seems to have mixed ferro- and antiferromagnetic exchange couplings. In the light of this, we extend the semiclassical treatment of the J1-J2 model to include ferromagnetic interactions, and present an analysis of the finite temperature properties of the model based on the exact diagonalization of 8, 16 and 20 site clusters. We propose that diffuse neutron scattering can be used to resolve the ambiguity inherent in determining the ratio and sign of J1 and J2 from thermodynamic properties alone, and use a finite temperature Lanczos algorithm to make predictions for the relevant high temperature spin-spin correlation functions. The possibility of a spin-liquid phase occurring for ferromagnetic J1 is also briefly discussed.