Beyond a phenomenological description of magnetostriction

Area of Science:

• Condensed Matter Physics
• Materials Science
• Ultrafast Magnetism

Background:

• Magnetostriction, the strain in magnetic materials due to magnetization changes, is typically understood phenomenologically.
• Its microscopic origin, the magnetoelastic stress, remains challenging to elucidate.
• Understanding magnetostriction at an atomistic level is crucial for advanced magnetic materials.

Purpose of the Study:

• To separate the spin and lattice responses in the time domain to understand magnetostriction's microscopic origin.
• To reveal the magnetoelastic stress generated during ultrafast demagnetization in FePt nanoparticles.
• To bridge the gap between phenomenological and atomistic descriptions of magnetostriction.

Main Methods:

• Utilized time-resolved X-ray diffraction to probe spin dynamics.
• Employed ultrafast electron diffraction to investigate lattice motion.
• Performed ab initio calculations to analyze electron and phonon stresses.

Main Results:

• Observed demagnetization in FePt nanoparticles with a time constant of 146 fs after laser excitation.
• Detected anisotropic, three-dimensional lattice motion following demagnetization.
• Quantified magnetoelastic stress by analyzing lattice motion characteristics and theoretical calculations.

Conclusions:

• Successfully separated spin and lattice dynamics in the time domain, providing an atomistic view of magnetostriction.
• Demonstrated that ultrafast demagnetization directly generates magnetoelastic stress.
• Opened new avenues for understanding and engineering magnetostrictive materials.