Different dimensionality trends in the Landau damping of magnons in iron, cobalt and nickel: time dependent density functional study

TL;DR

This study uses ab initio time-dependent density functional theory to analyze how the Landau damping of magnons varies with dimensionality in iron, cobalt, and nickel, revealing opposite trends in Fe and Ni and weak effects in Co.

Contribution

It provides a detailed theoretical investigation of dimensionality effects on magnon damping in transition metals using advanced first-principles methods.

Findings

In Fe, reducing dimensionality decreases damping.

In Ni, reducing dimensionality increases damping.

In Co, damping is weakly affected by dimensionality.

Abstract

We study the Landau damping of ferromagnetic magnons in Fe, Co, and Ni as the dimensionality of the system is reduced from three to two. We resort to the \textit{ab initio} linear response time dependent density functional theory in the adiabatic local spin density approximation. The numerical scheme is based on the Korringa-Kohn-Rostoker Green's function method. The key points of the theoretical approach and the implementation are discussed. We investigate the transition metals in three different forms: bulk phases, free-standing thin films and thin films supported on a nonmagnetic substrate. We demonstrate that the dimensionality trends in Fe and Ni are opposite: in Fe the transition from bulk bcc crystal to Fe/Cu(100) film reduces the damping whereas in Ni/Cu(100) film the attenuation increases compared to bulk fcc Ni. In Co, the strength of the damping depends relatively weakly on the sample dimensionality. We explain the difference in the trends on the basis of the underlying electronic structure. The influence of the substrate on the spin-wave damping is analyzed by employing Landau maps representing wave-vector resolved spectral density of the Stoner excitations.