Pchelkina Z V, Solovyev I V
M N Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, 620137, Ekaterinburg, Russia. Theoretical Physics and Applied Mathematics Department, Institute of Physics and Technology, Ural Federal University, Ekaterinburg 620002, Russia.
J Phys Condens Matter. 2015 Jan 21;27(2):026001. doi: 10.1088/0953-8984/27/2/026001. Epub 2014 Dec 11.
The effects of orbital degrees of freedom on the exchange interactions in a quasi-one-dimensional spin-1 antiferromagnet CaV2O4 are systematically studied. For this purpose a realistic low-energy electron model with the parameters derived from the first-principles calculations is constructed in the Wannier basis for the t2g bands. 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 differs substantially from the previously proposed phenomenological picture based on magnetic measurements and structural considerations, namely: (i) despite the quasi-one-dimensional character of the crystal structure, consisting of the zigzag chains of the 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 in exchange interactions in two crystallographically inequivalent chains. The combination of these three factors successfully reproduces the behaviour of experimental magnetic susceptibility.
系统地研究了轨道自由度对准一维自旋 - 1反铁磁体CaV₂O₄中交换相互作用的影响。为此，在t₂g能带的万尼尔基矢下，构建了一个具有从第一性原理计算得出的参数的实际低能电子模型。使用平均场基态附近的无穷小自旋旋转理论和超交换模型来计算交换相互作用，二者给出了一致的描述。所得到的交换相互作用行为与先前基于磁测量和结构考虑提出的唯象图像有很大不同，即：（i）尽管晶体结构为准一维，由边共享VO₆八面体的锯齿链组成，但电子结构本质上是三维的，这导致链之间存在有限的相互作用；（ii）沿链的支腿方向的交换相互作用似乎占主导；（iii）在两个晶体学不等价的链中，交换相互作用存在显著差异。这三个因素的组合成功地再现了实验磁化率的行为。
