September 6, 2024
- In a new paper, we describe an EUV transient grating experiment conducted at FERMI, in which we excited and detected coherent magnons with wavelengths as short as ~50 nm in a FeGd ferrimagnetic multilayer
- Magnons were generated by a pair of crossed EUV pulses with wavelenghts 25 - 42 nm and detected via diffraction of a probe EUV pulse at a wavelength of 8.34 nm tuned to the N45 edge of Gd.
- The intensity of the diffracted signal oscellates at the magnon frequency (Fig. 1). By varying the piump wavelength we vary the magnon wave vector and the frequency changes yielding magnon dispersion (Fig 2).
- This is the forst obserbvation of the excitation of magnons by EUV light and also the first observation of EUV scattering from amgnons.
- The results yield a new magnon spectroscopy technique bridging the wave vector gap between Brillouin light scattering and inelastic neutron scattering.
- Magnons with tens of nanometers wavelenght are of interest for the nascent field of magnonics. Out approach offers a unique way to excite such nanoscale magnons without fabricating nanostructures on the sample.
Fig. 1. (A) Experimental setup; (B) Sample schematic; (C) Images of the signal on the detector at different pump-probe time delays; (D) Integrated signal from the detector vs time delay showing magnon oscillations. The insert shows the initial ultrafast demagnetization dynamics.
Fig. 2 (A-B) Magnon oscillations at different wave vectors for two samples (labeled CMA and PMA) with different Fe/Gd composition; (C) measured magnon dispersion for the two samples. The highest wave vector corresponds to a magnon wavelength of 52.5 nm.
For more details, read the paper: