Itinerant and localized magnetization dynamics in antiferromagnetic Ho

TL;DR

This study uses femtosecond x-ray diffraction to explore how antiferromagnetic Ho's spin systems and lattice respond to ultrafast optical excitation, revealing rapid demagnetization and strong intra-atomic coupling.

Contribution

It provides the first direct, element-specific observation of the separate and combined dynamics of itinerant 5d and localized 4f electrons in antiferromagnetic Ho.

Findings

Demagnetization timescales similar to ferromagnetic 4f systems

Strong intra-atomic 4f-5d exchange coupling

Ultrafast lattice contraction due to magnetostriction release

Abstract

Using femtosecond time-resolved resonant magnetic x-ray diffraction at the Ho L3 absorption edge, we investigate the demagnetization dynamics in antiferromagnetically ordered metallic Ho after femtosecond optical excitation. Tuning the x-ray energy to the electric dipole (E1, 2p -> 5d) or quadrupole (E2, 2p -> 4f) transition allows us to selectively and independently study the spin dynamics of the itinerant 5d and localized 4f electronic subsystems via the suppression of the magnetic (2 1 3-tau ) satellite peak. We find demagnetization timescales very similar to ferromagnetic 4f systems, suggesting that the loss of magnetic order occurs via a similar spin-flip process in both cases. The simultaneous demagnetization of both subsystems demonstrates strong intra-atomic 4f-5d exchange coupling. In addition, an ultrafast lattice contraction due to the release of magnetostriction leads to a transient shift of the magnetic satellite peak.