Metal-free magnetism and spin caloritronics are at the forefront of condensed-matter physics. Here, the electronic structures and thermal spin-dependent transport properties of armchair graphene nanoribbons (N-AGNRs), where N is the ribbon width (N = 5-23), are systematically studied. The results show that the indirect band gaps exhibit not only oscillatory behavior but also periodic characteristics with E _3p > E_3p+1 > E_3p+2 (E _3p , E_3p+1 and E_3p+2 are the band gaps energy) for a certain integer p, with increasing AGNR width. The magnetic ground states are ferromagnetic (FM) with a Curie temperatures (T _C ) above room temperature. Furthermore, the spin-up and spin-down currents with opposite directions, generated by a temperature gradient, are almost symmetrical, indicating the appearance of the perfect spin-dependent Seebeck effect (SDSE). Moreover, thermally driven spin currents through the nanodevices induced the spin-Seebeck diode (SSD) effect. Our calculation results indicated that AGNRs can be applied in thermal spin nanodevices.

中文翻译：

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扶手椅石墨烯纳米带中的无金属磁性，自旋相关塞贝克效应和自旋塞贝克二极管效应。

无金属的磁性和自旋热电子学处于凝聚态物理的最前沿。在这里，系统地研究了扶手椅石墨烯纳米带（N-AGNRs）的电子结构和热自旋相关的输运性质，其中N是带的宽度（N = 5-23）。结果表明，间接带隙不仅表现出振荡行为，而且表现出周期性特征，其中E _3p > E _{3p + 1}  > E _{3p + 2}（E _3p，E _{3p + 1}和E _{3p + 2}是）一定的整数p，随着AGNR宽度的增加。磁性基态是铁磁性（FM），居里温度（T _C）高于室温。此外，由温度梯度产生的方向相反的向上和向下旋转的电流几乎是对称的，这表明出现了完全自旋相关的塞贝克效应（SDSE）。此外，通过纳米器件的热驱动自旋电流会引起自旋Seebeck二极管（SSD）效应。我们的计算结果表明AGNRs可应用于热自旋纳米器件。