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The MISTRAL beamline is one of the seven phase-I beamlines at the ALBA synchrotron light source (Barcelona, Spain) that will be opened to users at the end of 2010. MISTRAL will be devoted to cryotomography in the water window and multi-keV spectral regions for biological applications. The optics design consists of a plane-grating monochromator that has been implemented using variable-line-spacing gratings to fulfil the requirements of X-ray microscopy using a reflective condenser. For instance, a fixed-focus condition independent of the included angle, constant magnification as well as coma and spherical aberration corrections are achieved with this system. The reported design is of wider use. [ABSTRACT FROM AUTHOR]

The use of magnetic vector tomography/laminography has opened a 3D experimental window to access the magnetization at the nanoscale. These methods exploit the dependence of the magnetic contrast in transmission to recover its 3D configuration. However, hundreds of different angular projections are required leading to large measurement times. Here we present a fast method to dramatically reduce the experiment time specific for quasi two-dimensional magnetic systems. The algorithm uses the Beer-Lambert equation in the framework of X-ray transmission microscopy to obtain the 3D magnetic configuration of the sample. It has been demonstrated in permalloy microstructures, reconstructing the magnetization vector field with a reduced number of angular projections obtaining quantitative results. The throughput of the methodology is × 10–× 100 times faster than conventional magnetic vector tomography, making this characterization method of general interest for the community. [ABSTRACT FROM AUTHOR]

Thin perpendicular magnetic anisotropy films between two soft ferromagnetic layers have the nuclei for magnetization inversion at the bifurcations of their characteristic stripe domain pattern. The inverted nuclei induce vortex-antivortex pairs in the soft magnetic layers that exhibit a correlated motion extending several µm along the magnetic stripes during magnetization reversal. The sense of motion is completely determined by the topology of the magnetic bifurcations causing vortex-antivortex pairs to propagate in opposite senses depending on their polarities. This is a robust effect that might have practical applications. These findings are based on X-ray microscopy and micromagnetic calculations. [ABSTRACT FROM AUTHOR]

Optical elements of soft x-ray beamlines usually have motorized translations and rotations that allow for the fine alignment of the beamline. This is to steer the photon beam at some positions and to correct the focus on slits or on sample. Generally, each degree of freedom of a mirror induces a change of several parameters of the beam. Inversely, several motions are required to actuate on a single optical parameter, keeping the others unchanged. We define optical pseudomotors as combinations of physical motions of the optical elements of a beamline, which allow modifying one optical parameter without affecting the others. We describe a method to obtain analytic relationships between physical motions of mirrors and the corresponding variations of the beam parameters. This method has been implemented and tested at two beamlines at ALBA, where it is used to control the focus of the photon beam and its position independently. [ABSTRACT FROM AUTHOR]

• Stripe domains patterns have been observed in ferri/ferromagnetic multilayers. • Rare earth-transition metal alloys allow tuning the interactions between layers. • Transmission X-ray microscopy shows complex magnetic textures. The stacking of ferrimagnetic and ferromagnetic films leads to a competition between magnetic interactions that can stabilize Bloch points and other singularities at the interfaces. In this work, Gd x Co 1-x /NdCo 5 /Gd y Co 1-y trilayers, with different thicknesses, have been prepared. By tuning the stoichiometry of the Gd-Co outer layers, the Co magnetic sublattice dominates in one layer, whereas the opposite side is Gd dominated. In this way, in-depth magnetization domain walls can be created due to the balance between exchange and magnetostatic interactions. In addition, the weak perpendicular magnetic anisotropy of the Nd-Co central layer induces a stripe domain pattern, supporting the formation of Bloch points, meron-like textures, and vortex-antivortex pairs. The interaction between both types of structures, in-depth domain walls and magnetic singularities, has been studied by a combination of macroscopic Magneto-Optical Kerr Effect and Vibrating Sample Magnetometry measurements with microscopic Magnetic Force Microscopy and element selective magnetic Transmission soft X-ray Microscopy imaging. The results confirm marked changes in the magnetic properties of the trilayers, as compared with those single NdCo 5 films, and the formation of complex magnetic textures, associated with partial magnetization reversal, where magnetic singularities are formed. [ABSTRACT FROM AUTHOR]

Platelets of strontium hexaferrite (SrFe12O19, SFO), up to several micrometers in width, and tens of nanometers thick have been synthesized by a hydrothermal method. They have been studied by a combination of structural and magnetic techniques, with emphasis on Mössbauer spectroscopy and X-ray absorption based-measurements including spectroscopy and microscopy on the iron-L edges and the oxygen-K edge, allowing us to establish the differences and similarities between our synthesized nanostructures and commercial powders. The Mössbauer spectra reveal a greater contribution of iron tetrahedral sites in platelets in comparison to pure bulk material. For reference, high-resolution absorption and dichroic spectra have also been measured both from the platelets and from pure bulk material. The O-K edge has been reproduced by density functional theory calculations. Out-of-plane domains were observed with 180° domain walls less than 20 nm width, in good agreement with micromagnetic simulations. [ABSTRACT FROM AUTHOR]

Whereas a great deal of work is being devoted to magnetic singularities in two-dimensional (2D) systems (surfaces, interfaces, films) due to their possible applications, much less is known about their properties along the perpendicular direction. Here, we report on a pronounced asymmetry of the in-depth distribution of meronlike magnetic textures, which are magnetic singularities similar to 1/2 skyrmions, in magnetic layers. Meron textures are observed to be distributed in two groups defined by their topology. One of them resides almost exclusively at the top surface of the film and the other at the bottom one. This observation has been brought to light with element-specific magnetic transmission soft x-ray microscopy. Micromagnetic simulations reveal that closure domains are at the origin of this asymmetry. The result might be of general interest for controlling magnetic three-dimensional (3D) architectures. [ABSTRACT FROM AUTHOR]

A furnace covering the temperature range from 298 to 1300 K has been designed and constructed to study in situ the structural evolution of materials by using synchrotron X-ray microtomography. The furnace has cylindrical symmetry, compatible with the required 180° rotation, small dimensions and low absorption. It can also be used for other scattering methods, such as diffraction. [ABSTRACT FROM AUTHOR]