Employing soft x-ray resonant magnetic scattering to study domain sizes and anisotropy in Co/Pd multilayers

It is demonstrated that the magnetic diffraction pattern of the isotropic disordered maze pattern is well described utilizing a gamma distribution of domain sizes in a one-dimensional model. From the analysis, the mean domain size and the shape parameter of the distribution are obtained. The model reveals an average domain size that is significantly different from the value that is determined from the peak position of the structure factor in reciprocal space. As a proof of principle, a wedge-shaped (Co$_{tÅ}$/Pd$_{10Å}$)8 multilayer film, that covers the thickness range of the spin-reorientation transition, has been used. By means of soft x-ray resonant magnetic scattering (XRMS) and imaging techniques the thickness-driven evolution of the magnetic properties of the cobalt layers is explored. It is shown that minute changes of the domain pattern concerning domain size and geometry can be investigated and analyzed due to the high sensitivity and lateral resolution of the XRMS technique. The latter allows for the determination of the magnetic anisotropies of the cobalt layers within a thickness range of a few angstroms

Spatial coherence determination from the Fourier analysis of a resonant soft X-ray magnetic speckle pattern

We present a method to determine the two-dimensional spatial coherence of synchrotron radiation in the soft X-ray regime by analyzing the Fourier transform of the magnetic speckle pattern from a ferromagnetic film in a multidomain state. To corroborate the results, a Young’s double-pinhole experiment has been performed. The transverse coherence lengths in vertical and horizontal direction of both approaches are in a good agreement. The method presented here is simple and gives a direct access to the coherence properties of synchrotron radiation without nanostructured test objects

Terahertz Radiation Driven Dynamics of Magnetic DomainStructures Probed by Free-Electron Laser Light

Controlling magnetism on ultra-fast time scales and on nanometer lengthscales is a challenge for modern research in magnetism. Means for inducingdynamics on these time scales are femtosecond optical lasers [1] and THzsources [2]. Probing the dynamics on a nanometer length scale is possiblewith free-electron laser sources. We report on a THz-pump–XUV-probescattering experiment on (Co/Pt)n multilayers (n = 8,16) with perpendicularmagnetic anisotropy (PMA) exhibiting a maze domain pattern. An additionalelectromagnetic undulator available at FLASH was used to produce10-cycle linearly polarized THz pulses. The fundamental wavelength wasset to 150 μm and higher harmonics down to 30 μm have been used as apump. The resulting dynamics have been probed on femtosecond time scales[3] by resonant magnetic small-angle scattering at the cobalt M3 edge. For amultilayer with 8-fold repetition we observed that after 200 fs the scatteringintensity is drastically decreased by one order of magnitude (blue curve inFig. 1(a)). This change is fast compared to the duration of the THz pumppulse, which is about 6 ps long. Besides, a shift of the scattering peak positionto lower Q-values by 14% occurred (red curve in Fig. 1(a)). The latteris similar to what was found when using NIR pumping [4]. However, herewe observed an onset of the peak shift delayed by about 100 fs with respectto the reduction in scattering intensity and a different shape of both signals.Such subtle differences were impossible to resolve in the previous experimentsusing NIR-pump pulses due to the larger temporal jitter (> 100fs).Interestingly, the response is found to be much weaker (scattering intensity)or not resolvable (peak shift) in case of a Co/Pt multilayer with 16-foldrepetition (Fig. 1(b)). The major difference is the PMA of both samples.While the 16-fold multilayer has a strong PMA (K1,eff = 200kJ/m3) the 8-foldmultilayer has an almost vanishing PMA (K1,eff = 30kJ/m3), so that it is muchmore susceptible to magnetic fields and hence the THz magnetic field cancause a significant tilting of the magnetization.[1] E. Beaurepaire, J. Merle, A. Daunois, and J. Bigot, Phys. Rev. Lett. 76,4250 (1996). [2] C. Vicario, C. Ruchert, F. Ardana-Lamas, P.M. Derlet, etal. Nat. Photon. 7, 720 (2013). [3] F. Tavella, N. Stojanovic, G. Geloni, andM. Gensch, Nat Photon. 5, 162 (2011). [4] B. Pfau, S. Schaffert, L. Müller,C. Gutt, A. Al-Shemmary, et al., Nat. Commun. 3, 1100 (2012)

Characterization of Spatial Coherence of Synchrotron Radiation with Non-Redundant Arrays of Slits

A method for characterization of spatial coherence of X-ray radiation from a single diffraction pattern using non-redundant arrays of slits (NRA) is presented. Using NRAs the spatial coherence of the X-ray beam at the XUV X-ray beamline P04 of the PETRA III storage ring was measured

Characterization of Spatial Coherence of Synchrotron Radiation with Non-Redundant Arrays of Slits

A method for characterization of spatial coherence of X-ray radiation from a single diffraction pattern using non-redundant arrays of slits (NRA) is presented. Using NRAs the spatial coherence of the X-ray beam at the XUV X-ray beamline P04 of the PETRA III storage ring was measured