114 research outputs found
High Resolution Electron Microscopy of Radiation Defects in Ordered Alloys Induced by 1 MeV Electrons
Radiation defects induced by 1 MeV electrons in Zr_3Al, Au_3Cd and Au_3Mn have been investigated by high voltage high resolution electron microscopy. For the Ll_2 type intermetallic compound Zr_3Al, the changes in contrast of the superstructure images with electron irradiation suggest that the replacement disordering occurs in atom rows parallel to the incident beam. Neither dislocation loops nor voids are observed in the specimens damaged to 0.5 dpa. In the Au-Cd alloys, dislocation loops smaller than one nm in radius are identified at the electron irradiation of 2×10^ cm^. As for the Au-Mn alloys, dislocation loops are formed with preferential displacement of Mn atoms rather than Au atoms. The image contrast of irradiated Zr_3Al is discussed in comparison with the images computated by the multislice method
Real-space observation of short-period cubic lattice of skyrmions in MnGe
Emergent phenomena and functions arising from topological electron-spin
textures in real space or momentum space are attracting growing interest for
new concept of states of matter as well as for possible applications to
spintronics. One such example is a magnetic skyrmion, a topologically stable
nanoscale spin vortex structure characterized by a topological index.
Real-space regular arrays of skyrmions are described by combination of
multi-directional spin helixes. Nanoscale configurations and characteristics of
the two-dimensional skyrmion hexagonal-lattice have been revealed extensively
by real-space observations. Other three-dimensional forms of skyrmion lattices,
such as a cubic-lattice of skyrmions, are also anticipated to exist, yet their
direct observations remain elusive. Here we report real-space observations of
spin configurations of the skyrmion cubic-lattice in MnGe with a very short
period (~3 nm) and hence endowed with the largest skyrmion number density. The
skyrmion lattices parallel to the {100} atomic lattices are directly observed
using Lorentz transmission electron microscopes (Lorentz TEMs). It enables the
first simultaneous observation of magnetic skyrmions and underlying
atomic-lattice fringes. These results indicate the emergence of
skyrmion-antiskyrmion lattice in MnGe, which is a source of emergent
electromagnetic responses and will open a possibility of controlling
few-nanometer scale skyrmion lattices through atomic lattice modulations
Magnetic Domain of Fe
Magnetic flux in soft magnetic alloy Fe 73:5 Cu 1 Nb 3 Si 13:5 B 9 was investigated by electron holography coupled with a thickness mapping method. First the reconstructed phase image of a soft magnetic material with a simple wedge shape was simulated, and the contribution of both magnetic flux and inner potential to the reconstructed phase image was estimated. In the experiment, the magnetic flux was evaluated by removing the effect of inner potential with thickness mapping. The magnetic flux density of Fe 73:5 Cu 1 Nb 3 Si 13:5 B 9 obtained was 1.21 T which agreed well with that of a bulk specimen (1.28 T)
Discovery of a Bloch point quadrupole constituting hybrid topological strings
Topological magnetic (anti)skrymions are robust string-like objects heralded
as potential components in next-generation topological spintronics devices due
to their manipulability via low-energy stimuli such as magnetic fields, heat,
and electric/thermal current. While these two-dimensional (2D) topological
objects are widely studied, intrinsically three-dimensional (3D) electron-spin
real-space topology remains less explored despite its prevalence in bulky
magnets. Here, we capture the 3D structure of antiskyrmions in a
single-crystal, precision-doped (Fe_{0.63}Ni_{0.3}Pd_{0.07})_{3}P lamellae
using holographic vector field electron tomography at room temperature and zero
field. Our measurements reveal hybrid string-like solitons composed of
skyrmions with topological number W = -1 on the lamellae's surfaces and an
antiskyrmion (W = +1) connecting them. High resolution images uncover a Bloch
point (BP) quadrupole (four magnetic (anti)monopoles) positioned along the
rectangular antiskyrmion's four corners (Bloch lines), which enable the
observed lengthwise topological transitions. Furthermore, we calculate and
compare the energy densities of hybrid strings with ideal (anti)skyrmion
strings using micromagnetic simulations, which suggest that this composite
(anti)BP structure stabilizes via the subtle interplay between the
magnetostatic interaction and anisotropic Dzyaloshinskii-Moriya interaction.
The discovery of these hybrid spin textures enables topological tunabilty, a
tunable topological Hall effect, and the suppression of skyrmion Hall motion,
disrupting existing paradigms within spintronics.Comment: 11 pages, 4 main figures, 7 extended data figures, 1 extended data
tabl
糖尿病誘発性慢性腎疾患モデル動物―尿細管障害バイオマーカーによる検討―
Diabetes-induced chronic kidney disease( DCKD) is a serious health problem. Therefore, modalities for preventing/improving DCKD are required. The aim of this study was to establish an animal model of DCKD. Four five-week-old male OLETF and LETO rats were used as experimental and control animals, respectively. After both rats were raised 17 months, collections of urine, blood and bilateral kidneys were performed. Urinary biomarkers for renal proximal tubule injury, monocyte chemoattractant protein-1( MCP-1) and kidney injury molecule-1( KIM-1), were measured by the Bio-Plex system. OLETF rats showed a significant increase in blood glucose, Hb A1c, creatinine, blood urea nitrogen( BUN), kidney/body weight ratio, glomerular area, 24 h-urine volume, urinary protein concentrations, MCP-1 and KIM-1 compared with LETO rats. There was a positive correlation not only between BUN and MCP-1 or KIM-1 but also between urinary protein concentrations and MCP-1 or KIM-1. These results indicate that the present OLETF rats have both glomerular and proximal tubular injury. Thus, the aged male OLETF rats with long-term diabetes may become a potent animal model for examining effects of exercise/dietary therapies on DCKD
- …