Engineering elliptical spin-excitations by complex anisotropy fields in Fe adatoms and dimers on Cu(111)

TL;DR

This study explores how complex anisotropy fields influence elliptical spin excitations in Fe adatoms and dimers on Cu(111), revealing new ways to manipulate spin precession modes through material and magnetic configuration adjustments.

Contribution

The paper introduces a method to engineer elliptical spin excitations by modifying anisotropy fields, considering the effects of damping, magnetic coupling, and configuration on spin dynamics.

Findings

Elliptical precession can be induced via anisotropy energy manipulation.

The normal modes depend on magnetic configuration, changing with ferromagnetic or antiferromagnetic states.

Magnetic damping affects resonant frequencies and quantum fluctuations, especially in strongly biaxial and antiferromagnetic systems.

Abstract

We investigate the dynamics of Fe adatoms and dimers deposited on the Cu(111) metallic surface in the presence of spin-orbit coupling, within time-dependent density functional theory. The \textit{ab initio} results provide material-dependent parameters that can be used in semiclassical approaches, which are used for insightful interpretations of the excitation modes. By manipulating the surroundings of the magnetic elements, we show that elliptical precessional motion may be induced through the modification of the magnetic anisotropy energy. We also demonstrate how different kinds of spin precession are realized, considering the symmetry of the magnetic anisotropy energy, the ferro- or antiferromagnetic nature of the exchange coupling between the impurities, and the strength of the magnetic damping. In particular, the normal modes of a dimer depend on the initial magnetic configuration, changing drastically by going from a ferromagnetic metastable state to the antiferromagnetic ground state. By taking into account the effect of the damping into their resonant frequencies, we reveal that an important contribution arises for strongly biaxial systems and specially for the antiferromagnetic dimers with large exchange couplings. Counter intuitively, our results indicate that the magnetic damping influences the quantum fluctuations by decreasing the zero-point energy of the system.