Photon Factory Activity Report 2005 #23 Part B (2006)
Materials Science

4C/2005G141

Quantitative evaluation of quadrupole transition effect in ATS scattering frommagnetite, Fe3O4
Jun KOKUBUN*, Miyo KAWANA and Kohtaro ISHIDA
Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan
Introduction
ATS (anisotropic tensor of the susceptibility) scattering
can be observed in the forbidden Bragg reflections near
the absorption edge. This scattering is sensitive to theelectronic states in anisotropic environment, especially tothe direction of the electronic orbital. We have studied theATS scattering in iron pyrite (FeS2), magnetite (Fe3O4)
and so on.[1] These experimental results above the edge
are in good agreement with the calculation based on theelectric dipole transition. Below the edge, however, theeffects of quadrupole transition have been observed.
Magnetite has a spinel structure, in which the Fe atoms
occupy the tetrahedral A site and the octahedral B site.
The ATS scattering with dipole-dipole (d-d) transition
process is allowed for the B site but not allowed for the Asite because of the site symmetry. For the A site,therefore, we must consider more higher approximation,dipole-quadrupole (d-q) term. (For the B site the d-q
scattering is not allowed.) We previously studied theenergy and azimuthal angle dependence of the 002 and
006 forbidden reflections.[2] We observed two resonantpeaks in energy spectrum near the Fe K-absorption edge.
The main resonant peak is just above the edge and thesecond peak in the pre-edge region. From the differenceof the two reflection intensities we concluded that themain peak was mainly caused by d-d scattering from theB site and the pre-edge peak by d-q scattering from the A
site. However, we did not quantitatively evaluate eachcontribution because the azimuth dependence iscompletely same in both scattering. In the present report
we investigated the 046 forbidden reflection in order toestimate the quantitative contribution from the A and B
sites.

interference between the d-d and d-q scattering, where weused three parameters, absolute values of the anisotropic
tensorial element for the d-d and d-q scattering factors,f(dd) and f(dq), and the phase difference of these factors.
From the results we determined the ATS scatteringfactors; the f(dd) is 0.36 and the f(dq) is 0.22
electrons/atom at the main resonance, the f(dd) is 0.06
and the f(dq) is 0.21 electrons/atom at the pre-edge
resonance. Thus we have found that the d-q scatteringfrom the A site has relatively large effect on the bothresonance.

Fig. 1 Azimuthal angle dependence of the 046 forbidden
reflection at the main resonant energy, 7.119 keV.

Experimental Results
The experiment was carried out with a four-circle
diffractometer at BL4C, where the incident beam was σpolarized. The integrated intensity was measured for the046 forbidden reflection at different X-ray energies orazimuthal angles near the Fe K-absorption edge.
We observed the main and pre-edge resonant peaks
similar to those in the previous experiment. The figures 1and 2 show the azimuth dependence of the reflection at
the main and pre-edge resonant energies, respectively. In
these figures the circles denote the observations and thedashed line the calculation from the d-d or d-q scattering
only. As shown in these figures the observation at preedge resonance almost agrees with the d-q calculation,
while at the main resonance there is a little difference
between the observation and the d-d calculation. The
solid line is the result of curve fitting considering the136

Users' Report

Fig. 2 Azimuthal angle dependence of the 046 forbidden
reflection at the pre-edge resonant energy, 7.105 keV.
References[1] V. E. Dmitrienko et al.: Acta Cryst. A61 (2005) 481.
[2] M. Kanazawa et al.: J. Phys. Soc. Jpn. 71 (2002) 1765.
* kokubun@ph.noda.tus.ac.jp