Faster chiral versus collinear magnetic order recovery after optical excitation revealed by femtosecond XUV scattering

Abstract

While chiral spin structures stabilized by Dzyaloshinskii-Moriya interaction (DMI) are candidates as novel information carriers, their dynamics on the fs-ps timescale is little known. Since with the bulk Heisenberg exchange and the interfacial DMI two distinct exchange mechanisms are at play, the ultrafast dynamics of the chiral order needs to be ascertained and compared to the dynamics of the conventional collinear order. Using an XUV free-electron laser we determine the fs-ps temporal evolution of the chiral order in domain walls in a magnetic thin film sample by an IR pump - X-ray magnetic scattering probe experiment. Upon demagnetization we observe that the dichroic (CL-CR) signal connected with the chiral order correlator mzmx in the domain walls recovers significantly faster than the (CL + CR) sum signal representing the average collinear domain magnetization mz2 + mx2. We explore possible explanations based on spin structure dynamics and reduced transversal magnetization fluctuations inside the domain walls and find that the latter can explain the experimental data leading to different dynamics for collinear magnetic order and chiral magnetic order.

Observation of Magnetic Helicoidal Dichroism with Extreme Ultraviolet Light Vortices

“…Finally, the feasibility of this experiment with a FEL source naturally opens up the study of MHD in the time domain, as recently performed in nanoplasmonics [57,58]. MHD could then become a powerful experimental tool for the study of the ultrafast dynamics of magnetic materials and their topological properties [59,60], also way control and manipulate them, in a similar fashion as in the inverse Faraday effect with SAM [61].…”

Observation of magnetic helicoidal dichroism with extreme ultraviolet light vortices

“…Finally, the feasibility of this experiment with a FEL source naturally opens up the study of MHD in the time domain, as recently performed in nanoplasmonics [57,58]. MHD could then become a powerful experimental tool for the study of the ultrafast dynamics of magnetic materials and of their chiral properties [59,60], but also as a way to control and manipulate them, in a similar fashion as in the inverse Faraday effect with SAM [61]. This work was supported by: the Agence Nationale pour la Recherche (under Contracts No.…”

Symmetry-dependent ultrafast manipulation of nanoscale magnetic domains

“…Later studies in CoFe/Ni multilayers that could access higher order diffraction rings were able to disentangle domain-wall broadening from the periodicity, suggesting an ultrafast domain rearrangement [20]. More recently, a similar shift in the scattered ring was observed for chiral labyrinth domains [23,24]. This shift, however, has not been observed in stripe domains [17,19,25], apparently contradicting earlier works.…”

“…Traditionally, the time-dependent 2D scattering has been analyzed within a 1D representation achieved by azimuthal integration, either over the isotropic ring [16,20,23,24] or the anisotropic lobes [17,19]. However, our scattering data precludes this simple analysis, both because of the mixed isotropic-anisotropic scattering and because of the significant amount of data lost to the nonactive regions of the detector.…”