Single-pulse resonant magnetic scattering using a soft x-ray free-electron laser

We report on single-pulse resonant magnetic scattering experiments using soft x-ray pulses generated by the free-electron laser FLASH at DESY. We could record a magnetic diffraction pattern from a Co/Pt multilayer sample at the $\text{Co}{M}_{2,3}$ edge with a single 30-fs-long FEL pulse. The analysis of the magnetic small-angle scattering signal for subsequent pulses indicates a threshold energy density below which there is no indication that the magnetic properties of the sample might be altered.

Figure 1

(Color online) Schematics of the single-pulse magnetic scattering setup.

Figure 2

(Color online) Resonant magnetic small-angle scattering pattern of a Co/Pt multilayer recorded with a single 30 fs FEL pulse of $1.3\times {10}^{11}\text{W}{\text{cm}}^{-2}$. The photon wavelength was in resonance with the $\text{Co}{M}_{2,3}$ edge (20.8 nm) providing magnetic scattering contrast. The color scales indicates the number of scattered photons per pixel ($4\times 4\text{binned}$ image).

Figure 3

(Color online) Magnetic small-angle scattering patterns from six subsequent 30 fs illuminations of the same Co/Pt multilayer sample, from one single FEL pulse each. The time delay between the images is 10 s. The color scale indicates the number of scattered photons per pixel.

Figure 4

(Color online) The magnetic structure factor $S\left(Q\right)$ of the domain structure for different pulses as deduced from the CCD images.

Figure 5

(Color online) Top: maximum scattered intensity per pixel as a function of pulse number. Bottom: average magnetic domain size as a function of pulse number.

Figure 6

(Color online) Calculation of the temperature change in the magnetic multilayer sample 1 ps after irradiation by the FEL pulse as a function of lateral position $z$ in the sample (pulse energy $4\text{mJ}/{\text{cm}}^2$). For details see text. The FEL pulse is incident on the 50-nm-thick silicon nitride membrane from the left. The Pt seed layer starts at $z=50\text{nm}$.