1 Fully optical nanoscale switching 1

Ultra-fast control of magnetization driven by nanoscale light is key to achieving competitive bit sizes in next-generation data storage technology. Researchers at the Max Born Institute in Berlin and the large-scale Elettra facility in Trieste, Italy, have successfully demonstrated the ultra-rapid emergence of fully optical switching by generating a nanoscale network by two-pulse interference in the range. extreme ultraviolet spectral.

The physics of optically driven magnetization dynamics on the femtosecond time scale has become of great interest for two main reasons: first, to understand the fundamental mechanisms of non-equilibrium, ultra-fast rotational dynamics, and second, possible application in the next generation of information technology with a vision to meet the need for faster and more energy efficient data storage devices. Fully Optical Switching (AOS) is one of the most interesting and promising mechanisms for this effort, where the state of magnetization can be reversed between two directions with a single femtosecond laser pulse, which serves as “0s” and “1s “. While the understanding of AOS time control has progressed rapidly, knowledge about nanometer-scale ultrafast transport phenomena, important for the realization of fully optical magnetic inversion in technological applications, has remained limited due to the wavelength limitations of optical radiation. An elegant way to overcome these constraints is to reduce the wavelengths to the extreme ultraviolet (XUV) spectral range in transient grid experiments. This technique is based on the interference of two XUV beams leading to a nanoscale excitation pattern and has pioneered the EIS-Timer line of the FERMI Free Electron Laser (FEL) light in Trieste, Italy.

Researchers at the Max-Born-Institute in Berlin and the FEL FERMI facility have now excited a transient magnetic grid (TMG) with a periodicity of ΛTMG = 87 nm in a sample of ferrimagnetic GdFe alloy. The spatial evolution of the magnetization network was probed by the diffraction of a time-delayed third XUV pulse tuned to the N edge of Gd at a wavelength of 8.3 nm (150 eV). Because the AOS exhibits a strongly nonlinear response to excitation, changes in symmetry characteristic of the evolving magnetic grid other than the initial sinusoidal excitation pattern are expected. This information is encoded directly in the diffraction pattern: in the case of a linear magnetization response to excitation and without AOS, a sinusoidal TMG is induced and the second order of diffraction is suppressed. However, if AOS occurs, the shape of the lattice changes, now allowing a pronounced second-order diffraction intensity. In other words, the researchers identified the intensity ratio between the second and first order (R21) as an observable fingerprint for AOS in diffraction experiments.

In future transient grid experiments with significantly smaller periodicities up to <20 nm, ultrafast lateral transport processes are expected to balance the excitation gradients in a few picoseconds and therefore define the fundamental spatial limits of the AOS.

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Materials provided by the Max Born Institute for Nolinear Optics and Short Pulse Spectroscopy (MBI). Note: Content can be edited by style and length.

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