Spatio-temporal migration of antiferromagnetic domain walls in Sr2IrO4

TL;DR

This study uses advanced X-ray imaging to measure the rapid movement of antiferromagnetic domain walls in Sr2IrO4 during laser-induced demagnetization, revealing purely electronic spin dynamics at unprecedented speeds.

Contribution

It provides the first direct measurement of ultrafast antiferromagnetic domain wall migration driven by electronic spins in a Mott insulator.

Findings

Domain walls move at 3x10^6 m/s during demagnetization

Migration velocity exceeds acoustic velocities

Spin contribution dominates without lattice coupling

Abstract

By laser pump-probe time-resolved coherent magnetic X-ray diffraction imaging, we have measured the migration velocity of antiferromagnetic domain walls in the Mott insulator Sr2IrO4 at 100 K. During the laser-induced demagnetization, we observe domain walls moving at 3x10^6 m/s, significantly faster than acoustic velocities. This is understood to arise from a purely electronic spin contribution to the magnetic structure without any role for coupling to the crystal lattice.