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

8C2, 15B1, 15C /2004G261

XMLD study at the L2 edge of Gd in transmission methodwith the universal X-ray ellipsometer
Toru KURIYAMA*1, Yoshinori UEJI1, Yuki BISAIJI1, Kohei OKITSU2, Yoshiyuki AMEMIYA1,
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
1

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.

Fig. 1 XMCD spectrum obtained as Faraday rotation

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 muchsmaller compared to XMCD signal[1].
In our experiment, we attempted to detect XMLD
spectra at the L2 edge of Gadolinium (7930 eV). Gd islanthanoid, of which 4f shell is filled with 7 electrons. It
forms a hcp crystal structure, and is a simple ferromagnet
below the critical temperature Tc=297 K. XMLD
spectrum can be detected by measuring the so-called
Voigt rotation of polarization, originating from theasymmetry of absorption. We can also measure XMCD
spectrum from the so-called Faraday rotation, originatingfrom magnetic circular birefringence (MCB), which isconnected to MCD by K-K relation. Here, we focused
attention on the relation between XMCD and XMLDspectra. It is predicted that in the particular situation
XMLD spectra are proportional to the energy derivativeof XMCD spectra[1].
ExperimentalThe experiment was performed at BL-8C, with theX-ray ellipsometer. The sample was Gd polycrystal sheet,thickness of which was estimated to be about 4 µm. Itowas chilled to 4 C, and its magnetization axis wascontrolled by permanent magnet. At first themagnetization was saturated along the direction expected
to give the targeted signal, then along the direction
expected to reverse the sign. The difference of two signals
was extracted by removing other factors, such as rotation
originating from NLD and NCD.

Fig. 2 XMLD spectrum obtained as Voigt rotation
Results and Discussion
Figures 1 & 2 show XMCD and XMLD spectra,
respectively, which were obtained as the rotation of X-ray
polarization. The maximum rotations of XMCD andXMLD were about 1 mrad, 0.1 mrad, respectively. We
compared XMLD and XMCD spectra which weretransformed from the above spectra.
As wastheoretically predicted, the similarity was found between
XMLD spectrum and the energy derivative of XMCDspectrum.
In order to make quantitative discussion, it isnecessary to improve the accuracy of the experiment byincreasing data point and/or measuring time.
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)* kuriyama@x-ray.k.u-tokyo.ac.jp

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