Beyond a phenomenological description of magnetostriction

TL;DR

This study investigates ultrafast spin-lattice interactions in FePt nanoparticles, revealing anisotropic lattice dynamics that influence magnetic switching, with implications for future data storage technologies.

Contribution

It provides the first detailed time-resolved analysis of spin-lattice coupling in granular FePt, highlighting anisotropic lattice responses and their potential for magnetic switching.

Findings

Strong anisotropic lattice expansion and contraction observed

Lattice tetragonality increases and persists for tens of picoseconds

Results suggest new pathways for laser-assisted magnetic switching

Abstract

We use ultrafast x-ray and electron diffraction to disentangle spin-lattice coupling of granular FePt in the time domain. The reduced dimensionality of single-crystalline FePt nanoparticles leads to strong coupling of magnetic order and a highly anisotropic three-dimensional lattice motion characterized by a- and b-axis expansion and c-axis contraction. The resulting increase of the FePt lattice tetragonality, the key quantity determining the energy barrier between opposite FePt magnetization orientations, persists for tens of picoseconds. These results suggest a novel approach to laser-assisted magnetic switching in future data storage applications.