A finite spin life-time of conduction electrons may dominate Gilbert damping of two-dimensional metallic antiferromagnets or antiferromagnet/metal heterostructures. We investigate the Gilbert damping tensor for a typical low-energy model of a metallic antiferromagnet system with honeycomb magnetic lattice and Rashba spin-orbit coupling for conduction electrons. We distinguish three regimes of spin relaxation: exchange-dominated relaxation for weak spin-orbit coupling strength, Elliot-Yafet relaxation for moderate spin-orbit coupling, and Dyakonov-Perel relaxation for strong spin-orbit coupling. We show, however, that the latter regime takes place only for the in-plane Gilbert damping component. We also show that anisotropy of Gilbert damping persists for any finite spin-orbit interaction strength provided we consider no spatial variation of the Néel vector. Isotropic Gilbert damping is restored only if the electron spin-orbit length is larger than the magnon wavelength. Our theory applies to ${\mathrm{MnPS}}_3$ monolayer on Pt or to similar systems.

中文翻译：

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二维金属反铁磁体中的吉尔伯特阻尼

传导电子的有限自旋寿命可能主导二维金属反铁磁体或反铁磁体/金属异质结构的吉尔伯特阻尼。我们研究了具有蜂窝磁晶格和传导电子 Rashba 自旋轨道耦合的金属反铁磁体系统的典型低能模型的吉尔伯特阻尼张量。我们区分了三种自旋弛豫机制：弱自旋轨道耦合强度的交换主导弛豫、中等自旋轨道耦合的 Elliot-Yafet 弛豫和强自旋轨道耦合的 Dyakonov-Perel 弛豫。然而，我们表明后一种情况仅适用于面内吉尔伯特阻尼分量。我们还表明，只要我们不考虑尼尔矢量的空间变化，吉尔伯特阻尼的各向异性对于任何有限的自旋轨道相互作用强度都持续存在。仅当电子自旋轨道长度大于磁振子波长时，各向同性吉尔伯特阻尼才会恢复。我们的理论适用于${\mathrm{聚苯乙烯}}_3$Pt 上的单层或类似系统。