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We have studied the laser induced ultrafast quenching of Gd 4f magnetic order in ferrimagnetic Co100-xGdx alloys to highlight the role of the Co 3d–Gd 5d inter-atomic exchange coupling. We have taken advantage of the ultrashort soft X-ray pulses deliver by the femtoslicing beamline at the BESSY II synchrotron radiation source at the Helmholtz–Zentrum Berlin to perform element- and time-resolved X-ray Magnetic Circular Dichroism spectroscopy. Our results show that the laser induced quenching of Gd 4f magnetic order occurs on very different time-scales for the Co72Gd28, the Co77Gd23 and the Co79Gd21 alloys. Most of the magnetic moment losses occur within the first picosecond (ps) while the electron distribution is strongly out of equilibrium. After the equilibration of the electrons and lattice temperatures (t > 1 ps), the magnetic losses occur on slower rates that depend on the alloy composition: increasing the Co composition speeds up the demagnetization of Gd 4f sublattice. The strength of the Co 3d–Gd 5d inter-atomic exchange coupling which depends on composition, determines the efficiency of the angular momentum flow from the Gd 4f spin towards the lattice. Our results are in qualitative agreements with the predictions of the microscopic three temperatures model for ferrimagnetic alloys. [ABSTRACT FROM AUTHOR]

We have measured the hot-electron-induced demagnetization of a [Co/Pt]2 multilayer in M(x nm)/Cu(100 nm)/[Co(0.6 nm)/Pt(1.1 nm)]2 samples depending on the nature of the capping layer M and its thickness x. We found out that a Pt layer is more efficient than [Co/Pt]X, Cu, or MgO layers in converting infrared (IR) photon pulses into hot-electron pulses at a given laser power. We also found out that the maximum relative demagnetization amplitude is achieved for M(x) = Pt (7 nm). Our experimental results show qualitative agreement with numerical simulations based on the superdiffusive spin transport model. We concluded that the maximum relative demagnetization amplitude, which corresponds to the highest photon conversion into hot electrons, is an interplay between the IR penetration depth and the hot-electron inelastic mean free path within the capping layer. [ABSTRACT FROM AUTHOR]

A rich thermal magnetic phase diagram has been determined by magneto-optical Kerr magnetometry and microscopy in a He+ ion irradiated ultrathin Pt/Co(0.5 nm)/Pt film. The components of the net magnetization and the evolution and disappearance of the ribbonlike magnetic domain pattern have been studied in the perpendicular to in-plane spin reorientation transition temperature region. As observed in a dipolar frustrated ferromagnet, the ribbon pattern blurs progressively with increasing the temperature as due to efficient spatial fluctuations. We emphasize the limitation of present theories for interpreting such a type of dynamic transition. [ABSTRACT FROM AUTHOR]

We present an experimental study of all-optical helicity-dependent switching (AO-HDS) of ferromagnetic Pt/Co/Pt heterostructures with perpendicular magnetic anisotropy. The sample is patterned into a Hall cross and the AO-HDS is measured via the anomalous Hall effect. This all-electrical probing of the magnetization during AO-HDS enables a statistical quantification of the switching ratio for different laser parameters, such as the threshold power to achieve AO-HDS and the exposure time needed to reach complete switching at a given laser power. We find that the AO-HDS is a cumulative process, a certain number of optical pulses is needed to obtain a full and reproducible helicity-dependent switching. The deterministic switching of the ferromagnetic Pt/Co/Pt Hall cross provides a full "opto-spintronic device," where the remanent magnetization can be all-optically and reproducibly written and erased without the need of an external magnetic field. [ABSTRACT FROM AUTHOR]

The article presents a study on carbon contamination of soft X-ray beamlines. It mentions that carbon deposits in X-ray beamlines are know to absorb and scatter synchrotron radiation, which forbids efficient measurements. It notes that strong reflectivity losses are observed, wherein carbon absorptivity is small.

The article discusses how dynamic properties of materials present in time-resolved photoelectron spectroscopy can be studied using synchrotron radiation time structure. It presents a new experimental set-up installed on the TEMPO beamline of the SOLEIL synchrotron radiation source. It also modifies the electron energy analyzer, replacing the two-dimensional (2D) detection based on the presence of a phosphorous screen and a charge coupled device (CCD) camera with a delay-line 2D detector.