A local view of the laser induced magnetic domain dynamics in CoPd stripe domains at the picosecond time scale

TL;DR

This study investigates how femtosecond laser pulses induce reversible and irreversible changes in the magnetic stripe domains of CoPd using time-resolved X-ray magnetic circular dichroism microscopy, revealing thermal effects and domain reorganization.

Contribution

It provides the first real-space, time-resolved imaging of local magnetic domain transformations in CoPd under femtosecond laser excitation, highlighting threshold-dependent irreversible changes.

Findings

Irreversible domain transformations occur above 12 mJ/cm2 fluence.

Thermal effects reduce XMCD amplitude, affecting domain stability.

New organized magnetic domain patterns emerge after laser excitation.

Abstract

The dynamic of the magnetic structure in a well ordered ferromagnetic CoPd stripe domain pattern has been investigated upon excitation by femtosecond infrared laser pulses. Time-resolved X-ray magnetic circular dichroism in photoemission electron microscopy (TR-XMCD-PEEM) is used to perform real space magnetic imaging with 100 ps time resolution in order to show local transformations of the domains structures. Using the time resolution of the synchrotron radiation facility of the Helmholtz-Zentrum Berlin, we are able to image the transient magnetic domains in a repetitive pump and probe experiment. In this work, we study the reversible and irreversible transformations of the excited magnetic stripe domains as function of the laser fluence. Our results can be explained by thermal contributions, reducing the XMCD amplitude in each stripe domain below a threshold fluence of 12 mJ/cm2. Above this threshold fluence, irreversible transformations of the magnetic domains are observed. Static XMCD-PEEM images reveal the new partially ordered stripe domain structures characterized by a new local magnetic domain distribution showing an organized pattern at the micrometer scale. This new arrangement is attributed to the recovery of the magnetic anisotropy during heat dissipation under an Oersted field.