RESUMEN
Magnetic skyrmions are vortex-like topological spin textures often observed to form a triangular-lattice skyrmion crystal in structurally chiral magnets with the Dzyaloshinskii-Moriya interaction. Recently, ß-Mn structure-type Co-Zn-Mn alloys were identified as a new class of chiral magnet to host such skyrmion crystal phases, while ß-Mn itself is known as hosting an elemental geometrically frustrated spin liquid. We report the intermediate composition system Co7Zn7Mn6 to be a unique host of two disconnected, thermal-equilibrium topological skyrmion phases; one is a conventional skyrmion crystal phase stabilized by thermal fluctuations and restricted to exist just below the magnetic transition temperature Tc, and the other is a novel three-dimensionally disordered skyrmion phase that is stable well below Tc. The stability of this new disordered skyrmion phase is due to a cooperative interplay between the chiral magnetism with the Dzyaloshinskii-Moriya interaction and the frustrated magnetism inherent to ß-Mn.
RESUMEN
For diblockcopolymers of polybutadiene-poly(ethyleneoxide) (PB-PEO) type, water is a selective solvent. In dependence of the length of both blocks and the block length ratio, these polymers form a multitude of self-assembled structures in solution. In the present work scattering methods are used to investigate the water-soluble polymer PB125-PEO155 . It is found to form long rodlike micelles, which are characterized with respect to the aggregate length L , the cross sectional radius RCS , the radial scattering length density profile sigma r, and the radial aggregation number Nrad. Model-independent as well as model-based approaches are used for the scattering data analysis. From dynamic light scattering (DLS) and static light scattering (SLS) experiments the weight averaged length Lw of these stiff elongated aggregates is determined to Lw=350 nm . Small angle neutron scattering (SANS) reveals a cross sectional radius of RCS=17 nm and in combination with results from the SLS the radial aggregation number is found to be Nrad=70 .
RESUMEN
The present contribution presents the single-step preparation and characterization of poly(N-isopropyl acrylamide)-co-polystyrene core-shell microgels with varying polystyrene content. The swelling behavior of the particles is investigated using dynamic light scattering and differs significantly from the swelling behavior of poly(N-isopropyl acrylamide) homopolymer particles. The lower critical solution temperature is found to be shifted to lower temperatures upon increasing the polystyrene content of the particles. The core-shell structure of the particles is revealed by means of small angle neutron scattering (SANS) using the method of contrast variation. Additionally, the formation of mesoscopic crystals of these particles is investigated by means of scanning electron microscopy and also by SANS. The particles seem to have preferable properties with respect to crystallization compared to homopolymer microgels.
RESUMEN
Using small-angle neutron scattering, we have imaged the magnetic flux line lattice (FLL) in the d-wave heavy-fermion superconductor CeCoIn5. At low fields we find a hexagonal FLL. Around 0.6 T this undergoes what is most likely a first-order transition to square symmetry, with the nearest neighbors oriented along the gap node directions. This orientation of the square FLL is consistent with theoretical predictions based on the d-wave order parameter symmetry.
