Intrinsic damping phenomena from quantum to classical magnets: An ab initio study of Gilbert damping in a Pt/Co bilayer
Year: 2017
Type: article
Abstract: A fully quantum-mechanical description of the precessional damping of a Pt/Co bilayer is presented in the framework of the Keldysh Green's function approach using ab initio electronic structure calculations. In contrast to previous calculations of classical Gilbert damping (${\ensuremath{\alpha}}_{\mathrm{GD}}$), we demonstrate that ${\ensuremath{\alpha}}_{\mathrm{GD}}$ in the quantum case does not diverge in the ballistic regime due to the finite size of the total spin $S$. In the limit of $S\ensuremath{\rightarrow}\ensuremath{\infty}$ we show that the formalism recovers the torque correlation expression for ${\ensuremath{\alpha}}_{\mathrm{GD}}$ which we decompose into spin-pumping and spin-orbital torque correlation contributions. The formalism is generalized to take into account a self-consistently determined dephasing mechanism which preserves the conservation laws and allows the investigation of the effect of disorder. The dependence of ${\ensuremath{\alpha}}_{\mathrm{GD}}$ on Pt thickness and disorder strength is calculated, and the spin-diffusion length of Pt and the spin mixing conductance of the bilayer are determined and compared with experiments.
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2755779316