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

8C2,15B1,15C/2004G261

XMLD study at the L2 edge of Gd in transmission
with polarization switching method

Toru KURIYAMA*1, Yoshinori UEJI1, Yuki BISAIJI1, Takafumi
SHIMIZU1, Kohei OKITSU2,
1
Yoshiyuki AMEMIYA ,1
Department of Advanced Material Science, The University of Tokyo, Kashiwanoha, Kashiwa,Chiba 277-8561, Japan
2
Engineering Research Institute, The University of Tokyo, Yayoi, Bunkyo, Tokyo 113-8656, Japan
Introduction
X-ray magnetic linear dichroism (XMLD) is theabsorption difference for linearly polarized light (parallelor perpendicular to the magnetization), while X-ray
magnetic circular dichroism (XMCD) is absorption
difference for circularly polarized light (right-handed orleft handed). XMCD is known to be odd formagnetization M, i.e., it reverses its sign when M isreversed, therefore XMCD cannot be applied to antiferromagnetic materials. On the other hand, XMLD does
not change its sign when M is reversed, so it can beapplied to not only ferromagnetic but also antiferromagnetic materials.
The research on XMCD has been actively performed
because of its particular aspects (e.g., element selective,capable of separating orbital and spin magnetic moment),
and XMCD has become a useful tool for investigating
magnetic feature of materials. However, few XMLD
studies have been reported as yet [1], especially XMLD
spectra in transmission method[2,3]. One of the reasons
might be that XMLD signal is expected to be much small
compared to XMCD signal[1].
In our experiment, we attempted to detect XMLD
spectra at the L2 edge of Gadolinium (7930 eV). Gd islanthanoid, 4f shell of which is filled with 7 electrons. Itforms a hcp crystal structure, and is a simple ferromagnet
below the critical temperature Tc=297 K. We performed
this experiment using a universal X-ray ellipsometer, withpolarization switching mode. In addition to XMLD,XMCD is also measured because it is predicted that in theparticular situation (e.g. spherical symmetry for 3dtransition metals) XMLD spectra are proportional to theenergy derivative of XMCD spectra[1].
Experimental
The experiment was performed at BL-8C. The sample
was Gd polycrystal sheet, the thickness of which wasestimated to be about 3 µm. It was chilled to 4oC, and its
magnetization axis was controlled by permanent magnet.
At a fixed magnetization direction, X-ray beam isswitched between horizontal and vertical polarization for
XMLD, and between right- and left-handed circularpolarization for XMCD in turn, so as to detect thedichroic signals. The same experiments are made withsaturated magnetization axis changed to reverse thedichroic signals. The magnetic dichroism signals wasextracted by removing XNCD and XNLD. Measurements
was repeated 5 times at a fixed magnetization direction.

Fig. 1 XMCD spectrum

Fig. 2 XMLD spectrum
Results and Discussion
Figures 1 & 2 show XMCD and XMLD spectra. At themaximum XMCD shows about 0.2% of the edge jump,
and its spectrum coincides with previous result[4].
However, XMLD signal is buried in error bars and not solarge enough to make quantitative discussion.
In order to make quantitative discussion, the following
points should be considered in the next experiments.
Using a bragg reflection of smaller indices ofmonochromator in order to obtain more photon fluxUsing thinner and larger samples in order to obtainstronger transmission light
Using more brilliant light source
References[1] J. Kunes et al., Phys. Rev. B 67, 024431 (2003).
[2] J.B. Kortright et al., Phys. Rev. B 62, 12216 (2000).
[3]H.-Ch. Mertins et al., Phys Rev. Lett 87, 047401 (2001).
[4]G. Schütz et al, Z. Phys. B 73, 67 (1988).
* kuriyama@x-ray.k.u-tokyo.ac.jp

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