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

8C2/2004G261

Low-temperature X-ray ellipsometry with a liquid-helium cryostat
Yoshinori UEJI*1, Toru KURIYAMA1, Takafumi SHIMIZU 1, Takashiro AKITSU 2,Yoshiyuki AMEMIYA1
1
Department of Advanced Material Science, The University of Tokyo,
5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan2
Department of Chemistry, Keio University,
3-14-1 Hiyoshi,Yokohama 223-8522, Japan
Introduction
We have developed a universal X-ray ellipsometer
which consists of an X-ray polarizer, aberration-free
multiple phase retarders [1] and an analyzer. It enables us
to create an X-ray beam having a high degree (P > 0.98)
of linear, circular or other polarization state in the X-rayregion. It also enables us to analyze precisely thepolarization states of the beam transmitted or diffracted
by the specimen. The available X-ray energy range is 618 keV. With this system, we could measure NLD, NLB,NCD, NCB, MCD and MCB (Natural or Magnetic,
Circular or Linear, Dichroism or Birefringence) at room
temperature in the X-ray region.
Many of interesting materials cause magnetic phasetransition at low temperature. For example the cyanobridged 3d-4f heterobimetallic assembly
Nd(DMF)4 (H2O)3(µ-CN)Fe(CN)5⋅H2O (DMF = N, Ndimethylformamide) cause photoinduced magnetization
less than 50 K [2]. The photoinduced magnetization of
the Prussian blue is explained by the charge-transfer
mechanism. However, the photoinduced magnetization of
the 3d-4f heterobimetallic assembly isn’t cannot be
explained by the charge-transfer mechanism according toby Mossbauer spectra. As for this phenomenon, it ispredicted that an angle change of cyano combination is
would be related by single crystal structure analysis.
Therefore we introduced a liquid-helium cryostat intoa universal X-ray ellipsometry and aimed to analyze thephotoinduced magnetization of a 3d-4f heterobimetallic
assembly by NLD (polarized XAFS) and MCD byintroducing a liquid-helium cryostat into a universal Xray ellipsometry .
Development and Experimental
The liquid-helium cryostat for X-ray topography has
beenwas designed and manufactured (Fig. 1) [3]. The
cryostat is able to cool a sample from room temperature
to 4.2 K. The superconducting magnets were constructedin the cryostat, in which the directions of the magnetic
fields generated by a set of 3 independent coils wasgoniometrically controlled by 3 bipolar sources. The
maximum magnetic field is nearly equal to about 0.86 T.
We placed an optical fiber in the cryostat to irradiate asample with ultraviolet or visible rays to a sample. We
have measured the spectra of the NLD at Fe K-edge(7112 eV), Nd L2-edge (6722 eV) and Nd L3-edge (6208eV) with a 3d-4f heterobimetallic assembly single crystal
at room temperature as the preliminary measurements.
But, so far we We have not yet measured weren’t able toexperiment them at the low temperature for because ofleak trouble of vacuum.

Fig. 1 The liquid-helium cryostat
Results and discussions
We introduced a liquid-helium cryostat into a universal
X-ray ellipsometry. But, we weren’t able to experiment at
the low temperature for leak trouble of vacuum. We havemeasured the spectra of the NLD at Fe K-edge, Nd L2edge and Nd L3-edge with a 3d-4f heterobimetallic
assembly single crystal at room temperature.
The authors gratefully acknowledge are grateful to T.
Koide for the supply for of the liquid-helium cryostat.
Reference[1] K. Okitsu et al., J. Synchrotron Rad. 8, 33 (2001).
[2] G. Li et al., J. Am. Soc. 125, 12396 (2003).
[3] T. Nakajima, Physica B194-196, 143 (1994).
*ueji@k.u-tokyo.ac.jp

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