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arXiv 0709.2228cond-mat.str-el
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自旋为1/2的Heisenberg反铁磁体系Ba_2Cu(PO_4)_2和Sr_2Cu(PO_4)_2的电子结构

Electronic structure of spin 1/2 Heisenberg antiferromagnetic systems: Ba_2Cu(PO_4)_2 and Sr_2Cu(PO_4)_2

Sarita S. Salunke, M. A. H. Ahsan, R. Nath, A. V. Mahajan, I. Dasgupta

摘要:

采用第一性原理计算研究了低维磷酸盐Ba_2Cu(PO_4)_2和Sr_2Cu(PO_4)_2的电子结构和磁性.本文用自洽紧束缚线性Muffin-tin轨道方法和N阶Muffin-tin轨道方法计算了两种化合物中磁性离子Cu ~(2+)之间的各种链内和链间跳跃参数。我们发现最近邻的链内跳跃t是主要的相互作用,这表明化合物确实是一维的。通过对能带色散、轨道投影能带结构和跃迁参数的分析,证实了Cu ~(2+)-Cu ~(2+)超-超交换作用是沿晶体学b方向进行的,并以O-P-O为中介。我们还详细分析了这些系统的短程交换作用的起源。我们对Sr_2Cu(PO_4)_2与Ba_2Cu(PO_4)_2交换作用的比值的从头计算估计与已有的实验结果进行了很好的比较。

英文摘要:

We have employed first principles calculations to study the electronic structure and magnetic properties of the low-dimensional phosphates, Ba2Cu(PO4)2 and Sr2Cu(PO4)2. Using the self-consistent tight-binding lin- earized muffin-tin orbital method and the Nth order muffin-tin orbital method, we have calculated the various intrachain as well as the interchain hopping parameters between the magnetic ions Cu2+ for both the com- pounds. We find that the nearest-neighbor intrachain hopping t is the dominant interaction suggesting the compounds to be indeed one dimensional. Our analysis of the band dispersion, orbital projected band struc- tures, and the hopping parameters confirms that the Cu2+-Cu2+ super-super exchange interaction takes place along the crystallographic b direction mediated by O-P-O. We have also analyzed in detail the origin of short-range exchange interaction for these systems. Our ab initio estimate of the ratio of the exchange inter- action of Sr2Cu(PO4)2 to that of Ba2Cu(PO4)2 compares excellently with available experimental results.

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