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 ultra-fast 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 demagnetisation we observe that the dichroic (CL-CR) signal connected with the chiral order correlator $m_z{m}_x$ in the domain walls recovers significantly faster than the (CL+CR) sum signal representing the average collinear domain magnetisation $m_z^2+m_x^2$. We explore possible explanations based on spin structure dynamics and reduced transversal magnetisation 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.

arXiv comment28 pages, 14 figures

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Cited by in corpus (7)

• Evidence of extreme domain wall speeds under ultrafast optical excitation
• Driving spin chirality by electron dynamics in laser-excited antiferromagnets
• Theory of superdiffusive spin transport in noncollinear magnetic multilayers
• Laser-induced torques in spin spirals
• Observation of magnetic helicoidal dichroism with extreme ultraviolet light vortices
• Revealing domain wall stability during ultrafast demagnetization
• Chiral spin spiral in synthetic antiferromagnets probed by circular dichroism in x-ray resonant magnetic scattering