Photon Factory Activity Report 2004 #22 Part B (2005)
Crystallography

3A,10A/2003G183

Determination of spin orientations of five independent Fe sites
by resonant X-ray magnetic scattering
Takahiro AKI 1, Syoichi SAKURAI1, Norio SHIMIZU1, Koichi OHKUBO1, Kouji YAMAWAKI1,Takayasu HANASHIMA1, Takeharu MORI2, Takeshi TOYODA3, Satoshi SASAKI*1
1
Materials and Structures Lab., Tokyo Inst. Tech., Nagatsuta, Yokohama 226-0803, Japan
2
KEK-PF, Tsukuba, Ibaraki 305-0801, Japan3
Industrial Research Institute of Ishikawa, Kuratsuki, Kanazawa 920-8203, Japan
IntroductionResonant X-ray magnetic scattering (RXMS) has
attracted much interest as a useful tool to determine themagnetic structures associated with specific electronicstates such as 3d-4p interactions.
The diffraction
experiment in ferromagnetic Ni was first made at the Ni
K edge [1]. The resonant enhancement in the Bragg
intensity can be predicted between charge and magneticscatterings at the L edge of the rare-earth systems [2].
The large effect makes it possible for a tiny single-crystal
to give simultaneously a complete determination of thecrystal structure and spin arrangement.
In this study, M-type BaFe12O19 has been examined toconfirm the potential ability in magnetic structure
determinations, because there are five independent Fe
sites in a hexagonal-ferrite structure, which aretetrahedral 4f1, bipyramidal 2b, and octahedral 2a, 4f2 and12k sites.
Experimental
Preliminary diffraction experiments were carried out at
the BL-10A. RXMS experiments were performed at theFe K absorption edge at BL-3A. The horizontallypolarized white X-rays were monochromatized by theSi(111) double-crystal monochromator. The difference inthe Bragg intensities for right- and left-circularly
polarized X-rays was measured. The incident beam wasguided into a synthetic single crystal of (001) diamondwith a thickness of 0.492 mm in order to produce
circularly polarized X-rays. A standard four-circle
geometry was used around the Fe K edge. The incident
X-ray intensity was monitored with an ionizationchamber. The RXMS intensity was defined as an+++asymmetry ratio of R = (I - I )/( I + I ), where I and I are
the integrated Bragg intensities related to the right- andleft-circularly polarization.
Diffraction profiles for more than 30 reflections of asingle crystal of 0.07 mm in diameter were measured withright- and left-circularly polarized X-rays at room
temperature, which were produced passing through thephase retarder.
Results and discussion
X-ray magnetic circular dichroism (XMCD) spectra forthe same specimen were used to select some wavelengths
at the Fe K-absorption edge. The experimental resonant

202

Users' Reportmagnetic scattering factors were estimated from the K-K
transformation of XMCD spectra and the least-squarescalculation of observed integrated intensities.
The
estimation of magnetic scattering factors was made in thestructure-refinement procedure. The residuals of Σ (|Robs| 2|Rcalc| ) were minimized to fit the best parameters, where
Robs and Rcalc are observed and calculated ratios. The
variation of residual factors is plotted in Fig. 1 as amfunction of f " values.
The observed asymmetry ratios were in agreement withthose made for the most appropriate spin-orientation. The
schematic projection of the final crystal structure isshown in Fig. 2, indicating the magnetic moments.

Fig. 1: Variation of residual
mfactors versus f " values.

Fig. 2: Spin arrangement of Fe
ions in M-type BaFe12O19.
[010] projection with thevertical c axis.

References[1] K. Namikawa et al., J. Phys. Soc. Jpn. 54, 4099 (1985).
[2] P. Carra et al., Phys. Rev. B 40, 7324 (1989).

* sasaki@n.cc.titech.ac.jp