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arXiv 1410.7136cond-mat.mtrl-sci
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准一维反铁磁体CaV2O4交换作用的第一性原理研究

First principles investigation of exchange interactions in quasi-one-dimensional antiferromagnet CaV2O4

Z. V. Pchelkina, I. V. Solovyev

摘要:

系统地研究了自旋为1的准一维反铁磁体CaV 2 O 4中轨道自由度对交换相互作用的影响。为此,构造了一个实际的低能模型,其参数来自于第一性原理计算。交换相互作用的计算使用的理论的无穷小自旋旋转附近的平均场基态和超交换模型,这提供了一个一致的描述。所获得的交换相互作用的行为实质上不同于先前提出的基于磁性测量和结构考虑的唯象图像,即:(i)尽管晶体结构的准一维特征由边缘共享的VO 6八面体的锯齿形链组成,但电子结构基本上是三维的,这导致链之间的有限相互作用;(ii)沿链腿的交换相互作用似乎占主导地位;(iii)在两个晶体学上不等价的链中,交换相互作用存在实质性差异。这三个因素的组合成功地再现了实验磁化率的行为。

英文摘要:

The effect of orbital degrees of freedom on the exchange interactions in the spin-1 quasi-one-dimensional antiferromagnet CaV2O4 is systematically studied. For this purpose a realistic low-energy model with the parameters derived from the first-principles calculations is constructed. The exchange interactions are calculated using both the theory of infinitesimal spin rotations near the mean-field ground state and the superexchange model, which provide a consistent description. The obtained behaviour of exchange interactions substantially differs from the previously proposed phenomenological picture based on the magnetic measurements and structural considerations, namely: (i) Despite quasi-one-dimensional character of the crystal structure, consisting of the zigzag chains of edge-sharing VO6 octahedra, the electronic structure is essentially three-dimensional, that leads to finite interactions between the chains; (ii) The exchange interactions along the legs of the chains appear to dominate; and (iii) There is a substantial difference of exchange interactions in two crystallographically inequivalent chains. The combination of these three factors successfully reproduces the behaviour of experimental magnetic susceptibility.

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