搜索

x
中国物理学会期刊

自由基有机磁体中的孤子态研究

Soliton state in organic ferromagnets with spin radicals

PDF
导出引用
  • 自由基有机磁体结合了有机材料和磁性材料的优势,但自旋自由基的存在也使其内在元激发磁电特性异于传统有机半导体。本文基于Su-Schrieer-Heeger模型,考虑主链和自由基之间电子跃迁及电子-电子关联,研究了准一维自由基有机磁体中的孤子电荷自旋特性。结果表明,孤子能级和自旋分布依赖于自由基的悬挂模式。当自由基悬挂于主链偶数格点时,孤子态仅分布在主链奇数格点上,能带带隙中出现两条孤子浅能级,孤子态优选自旋与自由基自旋一致;而当自由基悬挂于主链奇数格点上时,孤子同时分布于主链和自由基,能带带隙中出现四条孤子浅能级,孤子优选自旋与自由基自旋取向相反。进一步通过电子态分析,阐明了不同自由基悬挂模式下孤子态与自由基的相互作用。该工作加深了人们对有机磁体中孤子元激发电荷自旋性质的理解。

     

    Organic ferromagnets with spin radicals combine the advantages of organic materials and magnetic materials, which are promising in the design of flexible organic spintronic devices. However, the presence of spin radicals makes the charge and spin properties of excitations different from those in normal organic materials. Based on the extended Su-Schrieffer-Heeger model including electron hopping, electron-lattice coupling and electron-electron interactions, we investigate charge and spin properties of solitons in finite quasi-one-dimensional organic ferromagnets with fixed-end boundary condition. The results demonstrate that the energy levels and spin density of the soliton depend on the hanging mode of the radicals on the main chain. When the radicals hang on the even-number sites of the main chain, the soliton state is localized only on odd-number sites of the main chain. Two shallow soliton levels appear in the band gap, and the preferential spin of the soliton is the same as that of the radicals. In contrast, when the radicals hang on the odd-number sites of the main chain, the soliton state distributes in both the main chain and radicals, where four shallow soliton levels emerge in the band gap. The preferential spin of the soliton is opposite to the radical spin. By analyzing the probability density of the soliton state, the mechanism of these phenomena is explained as the different interactions between the soliton state and radicals under different hanging modes of radicals, where the disturbance to the solitons from the antiferromagnetic spin density differs. The effect of different electron-electron interactions for the main chain and radicals are also discussed, where charge transfer between the main chain and radicals occurs and thus makes the charge density of the soliton nonzero. The work reveals the unique charge and spin properties of soliton excitations in organic magnets, which will be helpful for further design of organic spintronic devices.

     

    目录

    /

    返回文章
    返回