Optical control of 4f orbital state in rare-earth metals

TL;DR

This paper demonstrates optical control of the 4f orbital state in rare-earth metals, specifically Tb, using time-resolved X-ray techniques to influence magnetic anisotropy and magnetization dynamics.

Contribution

It reveals that optical pumping induces 4f-electronic excitations via inelastic 5d-4f scattering, altering orbital states and magnetic anisotropy in rare-earth metals.

Findings

Optical excitation causes 4f-electronic excitations in Tb.

Inelastic 5d-4f scattering drives orbital state changes.

Altered 4f orbitals impact magnetic anisotropy and dynamics.

Abstract

A change of orbital state alters the coupling between ions and their surroundings drastically. Orbital excitations are hence key to understand and control interaction of ions. Rare-earth (RE) elements with strong magneto-crystalline anisotropy (MCA) are important ingredients for magnetic devices. Thus, control of their localized 4f magnetic moments and anisotropy is one major challenge in ultrafast spin physics. With time-resolved X-ray absorption and resonant inelastic scattering experiments, we show for Tb metal that 4f-electronic excitations out of the ground state multiplet occur after optical pumping. These excitations are driven by inelastic 5d-4f-electron scattering, alter the 4f-orbital state and consequently the MCA with important implications for magnetization dynamics in 4f-metals, and more general for the excitation of localized electronic states in correlated materials.