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Magnetic skyrmions are topologically protected spin textures with promising prospects for applications in data storage. They can form a lattice state due to competing magnetic interactions and are commonly found in a small region of the temperature - magnetic field phase diagram. Recent work has demonstrated that these magnetic quasi-particles fluctuate at the μeV energy scale. Here, we use a coherent x-ray correlation method at an x-ray free-electron laser to investigate these fluctuations in a magnetic phase coexistence region near a first-order transition boundary where fluctuations are not expected to play a major role. Surprisingly, we find that the relaxation of the intermediate scattering function at this transition differs significantly compared to that deep in the skyrmion lattice phase. The observation of a compressed exponential behavior suggests solid-like dynamics, often associated with jamming. We assign this behavior to disorder and the phase coexistence observed in a narrow field-window near the transition, which can cause fluctuations that lead to glassy behavior.

Presented is an energy dissipation analysis framework for granular material that is based on thermodynamics. Theoretical formulations are derived from the second law of thermodynamics, in conjunction with a few plausible assumptions on energy transformation and dissipation. The role of plastic free energy is emphasized by a conceptual experiment showing its physical nature. Theoretical formulation is adapted in order to be applied in elastic–plastic finite element method (FEM) simulations. Developed methodology is verified through comparison of input work, stored energy, and energy dissipation of the system. Separation of plastic work into plastic free energy and energy dissipation removes a common mistake, made in a number of publications, where energy dissipation can attain negative values (energy production) which is impossible.

We report an x-ray photon correlation spectroscopy method that exploits the recent development of the two-pulse mode at the Linac Coherent Light Source. By using coherent resonant x-ray magnetic scattering, we studied spontaneous fluctuations on nanosecond time scales in thin films of multilayered Fe/Gd that exhibit ordered stripe and Skyrmion lattice phases. The correlation time of the fluctuations was found to differ between the Skyrmion phase and near the stripe-Skyrmion boundary. This technique will enable a significant new area of research on the study of equilibrium fluctuations in condensed matter.

The interesting physics and potential memory technologies resulting from topologically protected spin textures such as skyrmions have prompted efforts to discover new material systems that can host these kinds of magnetic structures. Here, we use the highly tunable magnetic properties of amorphous Fe/Gd multilayer films to explore the magnetic properties that lead to dipole-stabilized skyrmions and skyrmion lattices that form from the competition of dipolar field and exchange energy. Using both real space imaging and reciprocal space scattering techniques, we determined the range of material properties and magnetic fields where skyrmions form. Micromagnetic modeling closely matches our observation of small skyrmion features (∼50 to 70 nm) and suggests that these classes of skyrmions have a rich domain structure that is Bloch-like in the center of the film and more Néel-like towards each surface. Our results provide a pathway to engineer the formation and controllability of dipole skyrmion phases in a thin film geometry at different temperatures and magnetic fields.

Grazing-incidence small-angle X-ray scattering (GISAXS) is an important technique in the characterization of samples at the nanometre scale. A key aspect of GISAXS data analysis is the accurate simulation of samples to match the measurement. The distorted-wave Born approximation (DWBA) is a widely used model for the simulation of GISAXS patterns. For certain classes of sample such as nanostructures embedded in thin films, where the electric field intensity variation is significant relative to the size of the structures, a multi-slice DWBA theory is more accurate than the conventional DWBA method. However, simulating complex structures in the multi-slice setting is challenging and the algorithms typically used are designed on a case-by-case basis depending on the structure to be simulated. In this paper, an accurate algorithm for GISAXS simulations based on the multi-slice DWBA theory is presented. In particular, fundamental properties of the Fourier transform have been utilized to develop an algorithm that accurately computes the average refractive index profile as a function of depth and the Fourier transform of the portion of the sample within a given slice, which are key quantities required for the multi-slice DWBA simulation. The results from this method are compared with the traditionally used approximations, demonstrating that the proposed algorithm can produce more accurate results. Furthermore, this algorithm is general with respect to the sample structure, and does not require any sample-specific approximations to perform the simulations. This paper presents an accurate numerical algorithm for simulating grazing-incidence small-angle X-ray scattering patterns of nanostructures using the multi-slice distorted-wave Born approximation. The method overcomes the typical challenge of requiring the users to manually specify a way to approximate their samples by utilizing properties of Fourier transforms to automate the computation.

We show that properly engineered amorphous Fe-Gd alloy thin films with perpendicular magnetic anisotropy exhibit bound pairs of like-polarity, opposite helicity skyrmions at room temperature. Magnetic mirror symmetry planes present in the stripe phase, instead of chiral exchange, determine the internal skyrmion structure and the net achirality of the skyrmion phase. Our study shows that stripe domain engineering in amorphous alloy thin films may enable the creation of skyrmion phases with technologically desirable properties.

Ian P Sinha1, Sunil K Sinha21Division of Women’s and Children’s Health, Institute of Translational Medicine, University of Liverpool, Liverpool, UK; 2Department of Neonatology, University of Durham and James Cook University Hospital, Middlesbrough, UKAbstract: There is growing interest in the use of noninvasive methods of providing respiratory support to preterm infants, especially those born at the limits of viability. This paper relates to the use of noninvasive forms of respiratory support, which could be used to treat preterm infants with respiratory distress syndrome (RDS). Evidence is reviewed from clinical trials that have evaluated the use of continuous positive airway pressure (CPAP), nasal intermittent positive airway pressure (NIPPV), and high flow nasal cannulae (HFNC).Keywords: CPAP, NIPPV, RDS, preterm

The primary objective of this research work is to study the effect of surface treated coir geotextiles on the bearing behaviour of sand overlying clay model with geotextiles at the interface. Two woven and two non woven coir geotextiles were treated with bitumen emulsion and unsaturated polyester resin. The surface morphology and thermal stability were investigated by scanning electron micrograph and simultaneous thermal analyser respectively. The bearing ratio of sand overlying clay increased with treated woven/non woven coir geotextiles at the interface in soaked and unsoaked condition. The bearing ratio was higher for treated/untreated and woven/non woven coir geotextiles at the interface in unsoaked condition as compared to soaked condition. The chemical treatment improved the thermal stability of surface treated coir geotextiles through physical and chemical changes. [ABSTRACT FROM AUTHOR]

We have used neutron scattering techniques to examine the magnetic transitions in the Ho1-xErxRh4B4 pseudoternary system. A wide variety of behavior is found, ranging from mean-field behavior for HoRh4B4 to complicated behavior for ErRh4B4, where superconductivity and long-range ferromagnetic order coexist between 0.7 and 1.2 K. Long-range ferromagnetic order is found at the lowest temperatures for all alloy compositions. Alloys with more than about 30% Ho order magnetically along the c axis and superconductivity is destroyed in these alloys in a sharp transition coincident with magnetic ordering. Alloys near the ErRh4B4 composition order in the basal plane but undergo a complex ordering process through a sinusoidally modulated state. Because Ho and Er have competing orthogonal magnetic anisotropies, compounds near the composition Ho 0.25Er0.75Rh4B4 are near a multicritical point in the magnetic phase diagram.

Superconductivity and magnetism are two types of order that can take place in materials at low temperatures. When the magnetic order is ferromagnetic, a competition exists between magnetism and superconductivity. Neutron scattering has been used to measure the interaction of magnetism and superconductivity in a series of ternary rare-earth alloys. A wide range of behavior is found near the magnetic transition, including mean-field magnetic ordering, first-order transitions between magnetism and superconductivity, and co-existence of ferromagnetism and superconductivity with a sinusoidally-modulated magnetic phase. © 1983.

We have used neutron scattering techniques to examine the magnetic transitions in the Ho1-xErxRh4B4 pseudoternary system. A wide variety of behavior is found, ranging from mean-field behavior for HoRh4B4 to complicated behavior for ErRh4B4, where superconductivity and long-range ferromagnetic order coexist between 0.7 and 1.2 K. Long-range ferromagnetic order is found at the lowest temperatures for all alloy compositions. Alloys with more than about 30% Ho order magnetically along the c axis and superconductivity is destroyed in these alloys in a sharp transition coincident with magnetic ordering. Alloys near the ErRh4B4 composition order in the basal plane but undergo a complex ordering process through a sinusoidally modulated state. Because Ho and Er have competing orthogonal magnetic anisotropies, compounds near the composition Ho 0.25Er0.75Rh4B4 are near a multicritical point in the magnetic phase diagram.