Giant anisotropy of Gilbert damping in a Rashba honeycomb antiferromagnet

Abstract

Giant Gilbert damping anisotropy is identified as a signature of strong Rashba spin-orbit coupling in a two-dimensional antiferromagnet on a honeycomb lattice. The phenomenon originates in spinorbit induced splitting of conduction electron subbands that strongly suppresses certain spin-flip processes. As a result, the spin-orbit interaction is shown to support an undamped non-equilibrium dynamical mode that corresponds to an ultrafast in-plane Néel vector precession and a constant perpendicular-to-the-plane magnetization. The phenomenon is illustrated on the basis of a two dimensional s-d like model. Spin-orbit torques and conductivity are also computed microscopically for this model. Unlike Gilbert damping these quantities are shown to reveal only a weak anisotropy that is limited to the semiconductor regime corresponding to the Fermi energy staying in a close vicinity of antiferromagnetic gap. arXiv:1911.03408v1 [cond-mat.str-el]

Theory of tensorial Gilbert damping in antiferromagnets

“…In fact, the Gilbert damping in two sublattices can be different due to several effects e.g. spin pumping, domain wall motion, antiferromagnetic resonance width etc [58,59].…”