Anisotropic Ultrafast Spin Dynamics in Epitaxial Cobalt

TL;DR

This study reveals that in epitaxial cobalt thin films, ultrafast spin dynamics are anisotropic, with demagnetization and recovery times differing along magnetic axes due to magneto-crystalline anisotropy affecting electron-phonon interactions.

Contribution

It uncovers the role of anisotropic electron-lattice coupling in ultrafast magnetism through combined experimental and ab initio analysis.

Findings

35% slower demagnetization along the easy axis

Magneto-crystalline anisotropy influences electron-phonon coupling

Supports the role of anisotropic electron-lattice interactions in ultrafast spin dynamics

Abstract

We investigate the ultrafast spin dynamics in an epitaxial hcp(1100) cobalt thin film. By performing pump-probe magneto-optical measurements with the magnetization along either the easy or hard magnetic axis, we determine the demagnetization and recovery times for the two axes. We observe a 35% slower dynamics along the easy magnetization axis, which we attribute to magneto-crystalline anisotropy of the electron-phonon coupling, supported by our ab initio calculations. This points towards an unambiguous and previously undisclosed role of anisotropic electron-lattice coupling in ultrafast magnetism.