S. Komura

Magnetic properties of SrFe1-xCoxO3

Abstract Magnetic and neutron diffraction measurements have been made on the cubic perovskite-type SrFe 1- x Co x x O 3 . These oxides exhibit a helical spin configuration for 0 ⩽ x ≤ 0.1 and ferromagnetism for 0.2 ≤ x ⩽ 1. The results obtained indicate that Fe 4+ ions are nearly in a high-spin state.

A neutron spin echo spectrometer with two optimal field shape coils for neutron spin precession

Abstract We have designed and have been constructing at the C2−2 cold neutron guide port of JRR-3M, JAERI, a neutron spin echo spectrometer (NSE) which is equipped with two optimal field shape (OFS) coils for neutron spin precession with the maximum field integral of 0.22 T m, an assembly of position sensitive detectors (PSD), a converging polarizer and a wide area analyzer. The dynamic range of scattering vector Q covers from 0.005 A−1 to 0.2 A−1 and that of energy ħω from 10 neV to 30 μeV. Performance tests of the OFS coils show that the inhomogeneity of the magnetic field integral in the OFS coils with the spiral coils is so small that the NSE signal amplitude decreases little even for the neutron cross section of 30 ⊘mm diameter as the Fourier time t increases up to 25 ns, though the precession coils are close to iron covers of the neighboring neutron guide. This verifies that the OFS precession coils are appropriate for this NSE spectrometer. Another test experiment shows that the homogeneity condition of the precession magnet is loosened by use of PSD.

Dynamics of phase separation in binary systems

Abstract The present understanding of the dynamics of phase separation in various binary systems is reviewed and discussed in order to find universal aspects, such as scaling properties of the structure function, the evolution power law of the length scale, and the asymptotic behaviour of the structure function for small and large wave vector and the kinetics of kinks, interfaces and patterns. Emphasis is placed on how the early linear theories of phase separation have been developed, through non-linear theory, to the scaling theories and how computer simulation and experimental observations have confirmed such ideas on historical grounds. The importance of the acquisition of information about the microscopic atomic viewpoint and the macroscopic motion of phase boundaries, clusters and interfaces is stressed in order to advance investigations on this subject in the future.

Spin wave excitations in Fe2P

Abstract Spin wave excitations in Fe 2 P have been measured in order to investigate the interesting magnetic properties of this system. The spin wave enegies along [100] and [110] are not only much less than those along [001], but heavily softened with increasing temperature near the first order transition.

Structural evolution and microscopic interactions in a three‐component amphiphilic microemulsion system

Structures and interaction parameters of a three‐component amphiphilic microemulsion system consisting of n‐decane, water, and an amphiphile AOT (sodium‐di‐2‐ethylhexylsulfosuccinate) have been studied by means of small angle neutron scattering. The scattering curves are fitted with Teubuer and Strey’s formula, from which three structural parameters are extracted; the average periodic distance D between the oil and water, the structural correlation length ξ, and the area aH per amphiphile molecule. The same data are further examined in terms of Gompper and Schick’s formula, from which three interaction parameters are obtained; the strength of segregation J/T among the oil and water, the amphiphilicity L/T of the amphiphile toward the oil and water, and the critical surfactant volume fraction φcs. These interaction parameters have right order of magnitudes and their implications to structural evolution are discussed.

A model of magnetic inhomogeneous structure for Fe-Ni invar alloys

Abstract The magnetic inhomogeneous structure revealed by neutron small angle scattering for Fe-Ni Invar alloys can be interpreted in terms of a model in which an effective local concentration of Fe for each atom within a sphere is taken into account in order to determine the magnetic moment of the atom.

Neutron Small-Angle Scattering from Single-Walled Liposomes of Egg Phosphatidylcholine

Neutron small-angle scattering from single-walled liposomes of egg phosphatidylcholine in D2O solution has been measured in order to determine the geometry of the sonicated small liposomes. The results show that the inner and outer radii or the liposomes are 60 and 100 A, respectively, and that the statistical deviation or the radius amounts to 20% of the average value of the outer radius.

Small angle neutron scattering from Nd 15 Fe 77 B 11 8 and Nd 15 Fe 76 Al 1 B 11 8 permanent magnets

Domain walls, grain boundaries of sintered Nd 15 Fe 77 B 8 11and Nd 15 Fe 76 Al 1 B 8 11permanent magnets with different heat treatments have been examined by small-angle neutron scattering experiments. The results indicate that (1) there are many Bloch walls in the grains (Nd 2 Fe 14 B) which form a thin layer containing the c-axis of the tetragonal Nd 2 Fe 14 B, the thickness of which is ∼70A, and (2) there are film-like precipitates along the grain boundaries where thickness decreases from 60 A to 40 A by heat treatment at 600°C for 1 h after sintering, correlating with the coercive field increasing.

Evidence for the correlation of the magnetic inhomogeneous structure with the fluctuation of chemical composition in Fe-Ni Invar alloys

Abstract Small-angle scattering of polarized neutrons from Fe 65 62 Ni 35 Invar alloys was performed to demonstrate the correlation of the magnetic inhomogeneous structure with the fluctuation of the chemical composition. The result supports our previously proposed model in which the Ni-rich local regions tend to be ferromagnetic and the Fe-rich local regions paramagnetic.

Polarized neutron diffraction study on CoMnP single crystal

Abstract Polarized neutron diffraction measurements have been done on CoMnP single crystals at room temperature. The magnetic moments on the tetrahedral Co I and pyramidal Mn II atoms are 0.06μ B and 2.66μ B , respectively. The observed magnetic form factor suggests that the unpaired 3d-electrons are quasi-localized on the atoms.