Fig. 1: Magnetic excitations in the Fe L₃ − edge RIXS spectra of Fe_4.75GeTe₂.

a Fe_4.75GeTe₂crystal structure drawn using VESTA⁵⁴. A single unit cell contains three Fe-Ge-Te slabs. b Schematic of RIXS experimental geometry. In the hexagonal structure representation, two orthogonal wave vectors—(100) and (001)—form the scattering plane highlighted in pink. θ is an angle between the incident X-ray and the (100) axis while Ω is the scattering angle between incoming and outgoing X-ray. The double-headed arrow represents the π polarization of the incident light. c Fe L_3,2- edge XAS measured at θ = 15^∘ in total electron yield (TEY) mode at 70 K. A solid vertical line represents the Fe L₃-edge maximum, that corresponds to the incident photon energy (707.9 eV) used for the RIXS spectra. d RIXS intensity map measured as a function of incident photon around the Fe L₃—edge, and zoomed in to cover excitations below 300 meV. For this dataset, θ = 20^∘ and Ω = 95^∘ corresponding to Q = (−0.16 0 2.17). e, f Two representative RIXS scans (black dotted line) at (−0.35 0 1.4) and (−0.3 0 1.74). The low-energy excitations are fitted with an elastic peak (gray), a phonon (blue), a magnon (red), a broad continuum, and a background (gray line) stretching to higher energies. The red solid line represents the fit sum. The inset in (e) shows the measured Fe₅GeTe single crystal. All RIXS spectra displayed in this work were measured at T = 70 K, using π polarization. The error bars of the RIXS spectra are defined assuming a Poisson distribution of the single-photon counted events.