Fumitake Itoh

Magnetic XANES of circularly polarized X-ray absorption on Fe and Ni metals and Nd2Fe14B compound

Magnetic effects in the X-ray absorption process have been measured using circularly polarized X-rays emitted from an elliptical multipole wiggler. Magnetic XANES spectra on the K -edge of Fe and Ni taken by the transmission method show positive and negative spin polarizations, respectively, near the Fermi level which are consistent with the results in literature. A large positive magnetic XANES spectrum on the Nd L 2 -edge of Nd 2 Fe 14 B compound measured by the fluorescent method indicates that the unoccupied 5 d -bands are polarized due to a significant hybridization between 4 f - and 5 d -states. The magnetic XANES spectrum on the Nd L 3 -edge has a structure below the Fermi level, suggesting a quadrupole transition contribution of the partially vacant majority band of 4 f -states.

Circular magnetic X-ray dichroism at the K-absorption edge in Fe-Ni alloys

The first systematic measurements of circular magnetic X-ray dichroism (CMXD) effects at the K -edge in 3 d -transition metal alloys have been made in Fe–Ni alloy over a wide composition range. It has been found that the CMXD spectrum at the Fe K -edge is similar to that at the Ni K -edge in each alloy, indicating that the CMXD spectra at the K -edge mainly reflect an itinerant character of 4 p -states. The features of the CMXD spectra correspond to those of X-ray absorption near-edge structure (XANES) spectra, reflecting the change of crystal structure. The signal intensities around the absorption edge energy, E 0 , have strong Ni concentration dependence, suggesting a close relationship between the CMXD effects around E 0 and the spin polarization of 3 d -states.

γ-Ray Compton Profiles of Lithium and Sodium in the Liquid and Solid State

The Compton profiles of lithium and sodium in both liquid and solid states have been measured using 59.54-keV γ-rays from 1Ci 241 Am. A clear difference of the Compton profile between the liquid and solid states has been found in lithium and sodium, respectively. The experimental Compton profiles corrected for the multiple scattering are compared with various theoretical profiles of these elements in both liquid and solid states.

Compton Scattering Study of Electron Momentum Density in Vanadium

The [100], [110] and [111] Compton profiles of vanadium are measured with a momentum resolution of 0.12 atomic units. The observed profiles have fine structures and directional anisotropies. Comparison of the results with the APW band theoretical predictions shows that the band theory overestimates the momentum density at low momenta and underestimates it at high momenta. The theory also overemphasizes the fine structures and the scale of the anisotropies.

Anisotropies of magnetic Compton profiles in Co∕Pd multilayer system

Anisotropies of spin-projected wave functions are measured on a Pd∕Co multilayer system by measuring magnetic Compton profiles. The anisotropies of the wave functions are decomposed into the contributions of Co 3d states and Pd 4d states using an atomic model by a Hartree-Fock calculation assuming uniaxial (cylindrical) symmetry. Perpendicular anisotropy in Pd∕Co multilayers is dominated by the anisotropy of Co 3d states; states with both magnetic quantum number ∣m∣=2 and ∣m∣=1 contribute.

Water-cooled quasi-doubly bent crystal monochromator for Compton scattering experiments

Commissioning and performance of a water‐cooled quasi doubly bent crystal monochromator for Compton scattering experiments are described. The monochromator consists of an array of twenty singly bent crystals. Each crystal is half immersed in liquid Ga‐ln alloy contained in a water‐cooled holder. This is necessary because the monochromator must be able to withstand heat load of 4 kW from synchrotron radiation from an ellipsoid multipole wiggler at the 6.5 GeV accumulation ring. The alignment procedure for twenty singly bent crystals is described in detail. Its performance is as follows; the focused beam size of 60 keV x rays is about 3 mm (vertical) and 8 mm (horizontal). The flux is 6×1012 photons/s at stored currents of 30 mA and the energy resolution is 88 eV for 60 keV x rays. Heating of various adjusting mechanisms by Compton scattered x rays from both the absorber used to suppress low energy x rays and the monochromator crystals is found to be a very serious problem for designing a high energy x‐ray ...

Experimental and Monte Calro Studies of Multiple Scattering Correction in the Compton Profile Aluminum

The Monte Carlo method for correcting the effect of multiple scattering in Compton profile measurements has been extended to take account of the geometry of collimators. This procedure is applied to experimental Compton profiles of aluminum measured with 59.54 keV γ-rays for various sample thickness. It is found that the corrected Compton profiles are independent of the sample thickness within experimental errors. Three theoretical Compton profiles for aluminum are compared with the experimental one.

X-Ray Magnetic Form Factor of UTe

A measurement of the magnetic form factor of a ferromagnetic actinide compound of UTe with circularly polarized X-rays is reported. The present geometrical configuration of the measurement gives a form factor of L ( k )+0.3 S ( k ), where L ( k ) and S ( k ) are the form factors of the orbital and the spin magnetic moment, respectively. We have combined the X-ray magnetic form factor with the neutron one which gives L(k)+2S(k) (G. Busch e t a l .: J. Phys. C 12 (1979) 1391), and have deduced L ( k ) and S ( k ) separately. The obtained profiles of L ( k ) and S ( k ) show that the orbital and the spin magnetic moments are spatially spread out more than those calculated for a free uranium ion.

Application of circularly polarized x-rays to magnetic Compton-scattering experiments

Abstract Magnetic Compton-scattering experiments are successfully applied to the measurement of the electron-spin densities of Fe and Ni metals in momentum space. Circularly polarized 60-keV X-rays emitted from an elliptical multipole wiggler installed at the 6.5-GeV storage ring of National Laboratory for High Energy Physics (KEK) were used in these experiments. The highest statistical accuracy ever achieved is obtained. The results of ferromagnetic Fe and Ni are compared with recent band-theoretical magnetic Compton profiles calculated by Kubo and Asano using the full-potential linearized augumented-plane-wave method. Contrary to previous investigations, excellent agreement is found between the experiment and the theory. This paper also gives a brief introduction of the Compton profile, following the aim of the symposium.

X-ray magnetic circular dichroism on Co monodispersive cluster assemblies

X-ray absorption near edge structure (XANES) spectra and x-ray magnetic circular dichroism (XMCD) spectra at the Co K edge have been measured for Co clusters with the mean diameter d = 6-13 nm. The spectral analysis indicates that the fcc phase is predominant for d = 6 nm, while the hcp phase gradually increases with increasing d in agreement with the results of transmission electron microscopy. The 4p orbital moments of clusters tend to decrease in the smaller cluster, but the reduction is small compared with the case of the multilayers, suggesting the importance of surface effects of the Co cluster system.