Fingerprint of vortex-like flux closure in isotropic Nd-Fe-B bulk magnet

Taking advantage of recent progress in neutron instrumentation and in the understanding of magnetic-field-dependent small-angle neutron scattering, here, we study the three-dimensional magnetization distribution within an isotropic Nd-Fe-B bulk magnet. The magnetic neutron scattering cross section of this system features the so-called spike anisotropy, which points towards the presence of a strong magnetodipolar interaction. This experimental result combined with a damped oscillatory behavior of the corresponding correlation function and recent micromagnetic simulation results on spherical nanoparticles suggest an interpretation of the neutron data in terms of vortex-like flux closure patterns. The field-dependent correlation length is very well reproduced by a power-law model used to describe the London penetration depth in the vortex state of type-II superconductors and suggests the 'pairing' (interaction) of magnetic vortices.Comment: 14 pages, 5 figure

Temperature dependence of nanostructure in PbSe–ZnSe composite thin film

The nanostructure of PbSe–ZnSe composite thin films prepared by the hot-wall deposition (HWD) method was investigated using small-angle x-ray (SAXS) scattering. The SAXS profiles indicate the formation of two kinds of nanoparticles: large nanoparticles that vanish and small particles that increase in size with increasing temperature. At high substrate temperatures, the volume fraction of all the nanoparticles estimated from SAXS is consistent with that of PbSe obtained by chemical analysis. This shows that PbSe forms nanoparticles at high substrate temperatures. On the other hand, the same analysis for the volume fraction at low substrate temperatures reveals that the chemical composition of the nanoparticles differs from PbSe. Pb nanoparticles are probably formed at low substrate temperatures and disappear with increasing substrate temperature

Nanostructure characterization of Co–Pd–Si–O soft magnetic nanogranular film using small-angle X-ray and neutronscattering

The nanostructure of a Co–Pd–Si–O nanogranular film was investigated with the combined use of small-angle x-ray (SAXS) and neutron scattering (SANS). Using a new, compact type of SANS instrument, the SANS profiles of individual particles with a diameter of about 2–4 nm were successfully observed. The structures of magnetic regions were found to be the same as the chemical structures of the particles, and a sharp interface was observed between the matrix and the particles. The SAXS to SANS ratio clearly indicates that the particles are a CoPd alloy and the matrix is not pure SiO2. In fact, the matrix is composed of a meaningful amountof Co

Neutron imaging for magnetization inside an operating inductor

Abstract Magnetic components are key parts of energy conversion systems, such as electric generators, motors, power electric devices, and magnetic refrigerators. Toroidal inductors with magnetic ring cores can be found inside such electric devices that are used daily. For such inductors, magnetization vector M is believed to circulate with/without distribution inside magnetic cores as electric power was used in the late nineteenth century. Nevertheless, notably, the distribution of M has never been directly verified. Herein, we measured a map of polarized neutron transmission spectra for a ferrite ring core assembled on a familiar inductor device. The results showed that M circulates inside the ring core with a ferrimagnetic spin order when power is supplied to the coil. In other words, this method enables the multiscale operando imaging of magnetic states, allowing us to evaluate the novel architectures of high-performance energy conversion systems using magnetic components with complex magnetic states

Commissioning of Versatile Compact Neutron Diffractometer (VCND) at the B-3 Beam Port of Kyoto University Research Reactor (KUR)

Proceedings of the 3rd J-PARC Symposium (J-PARC2019)Owing to successful promotion of the research and education by Kyoto University Research Reactor (KUR), a versatile compact neutron diffractometer (VCND) was designed and built at the B-3 beam port of KUR. With a monochromatic beam of neutrons (wavelength, λ = 1.0 Å), neutron diffraction data can be collected in the scattering angle, 2θ, range of 5–130°. The resolution of the VCND, Δd/d, is approximately 1%, evaluated from the neutron diffraction data of diamond powder. As the first results of the VCND, we demonstrated structural analyses of the following energy storage materials and functional materials: strontium fluoride (SrF₂), lanthanum-nickel intermetallic alloy (LaNi₅), and an austenitic-ferritic stainless steel