16A1 BM - Tender X-ray Absorption, Diffraction
The Ru Electron Configuration of Grain-aligned Powder RuSr2GdCu2O8 and Fe K-edge of
Sm1-xLaxFeAsO1-yFy
T.-J. Shiu (許彩珍)1, C.-H. Hsu (徐晨軒)1, B.-C. Chang (張炳章)1,
H.-C. Ku (古煥球)1, and L.-Y. Jang (張凌雲)2
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
2
National Synchrotron Radiation Research Center, Hsinchu, Taiwan
(110)
(220)
(200)
(b) ~ab-plane // Ba (hk0)
0
5
(006)
(005)
(004)
(003)
(002)
(c) ~c-axis // rotation axis (00l)
(113)
epoxy
0
epoxy
10
15
20
25
30
2θ (degree)
35
40
45
50
Fig. 1: XRD of grain-aligned powder RuSr2GdCu2O8.
The angle dependence of normalized Ru L3-edge
(2p-4d dipole transition) XANES at 300 K for grainaligned powder RuSr2GdCu2O8 and RuSr2EuCu2O8 were
shown in Fig. 2. The threshold energy Eo is almost
identical for the different incident polarization angle
between the c-axis. The peak A is the transition from
2p3/2 to 4d-t2g and peak B is the transition from 2p3/2 to
4d-eg. The energy separation E = 2.6 eV for
RuSr2GdCu2O8 and smaller than 3.2 eV for Sr2GdRuO6,
which indicates a mixed-valence Ru4/5+ character. [1, 2]
0.8
RuSr2GdCu2O8
A (4d-t2g)
B (eg)
Ru L3-edge XANES
(2p3/2 -> 4d bands)
0
30
45
60
80
0.6
0.4
E0 -> 2839.6 eV
0.2
0.0
2820
2825
2830
2835
2840
2845
1.0
B (eg)
A (4d-t2g)
o
0
o
30
o
45
o
60
o
80
0.8
0.6
0.2
Ru L3-edge XANES
(2p3/2 -> 4d bands)
2825
2830
2835
2840
2845
2850
Derivative absorption intensity
Normalized absorption intensity
SmFeAsO1-xFx
Fe K-edge XANES
(1s -> 4p bands)
0.4
Fe
0.2
0.0
7100
7110
7120
7130
Photon energy E (eV)
x=
0.05
0.25
0.30
0.35
0.40
7140
7150
0.4
0
45
80
Fe
0.2
7120
7140
7160
7180
7120.0 eV
7111.8 eV
Fe K-edge XANES
(1s -> 4p bands)
7116.6 eV
Fe
o
0
o
45
o
80
0.0
7100
7110
7120
7130
7140
Photon energy E (eV)
1.2
SmFeAsO1-xFx
7112 eV
0.15
7120 eV
Fe K-edge XANES
(1s -> 4p bands)
7116.8 eV
7111.4 eV
0.10
7119.4 eV
Fe
0.05
7105
7110
7115
7120
7125
7130
7135
Sm0.95La0.05FeAsO0.85F0.15
0.8
Fe K-edge XANES
(1s -> 4p bands)
εF
0.4
0.0
7105
x=
0.05
0.25
0.30
0.35
0.40
Fe metal
300 K
100 K
10 K
7110
7115
7120
7125
Photon energy E (eV)
Fig. 5: Fe-K edge XANES for grain-aligned powder
Sm0.95La0.05FeAsO0.85F0.15 at 10, 100, 300 K.
0.00
-0.05
7100
Fe K-edge XANES
(1s -> 4p bands)
Sm0.95La0.05FeAsO0.85F0.15
7112.0 eV
Fig. 4: Fe-K edge XANES for grain-aligned powder
Sm0.95La0.05FeAsO0.85F0.15.
Fe-K edge of Sm0.95La0.05FeAsO0.85F0.15 at different
temperature was shown in Fig. 5. The change of electron
configuration is not obvious at the different temperature.
0.20
0.6
0.6
Photon energy E (eV)
Fig. 2: Ru L3-edge XANES for grain aligned powder
RuSr2GdCu2O8 and RuSr2EuCu2O8.
The K-edge of Cl was observed at 2822 eV,
indicating the existence of chlorine in epoxy. The two
types of AB epoxy exhibit the different absorption ratio.
The former is smaller than the latter.
0.8
Sm0.95La0.05FeAsO0.85F0.15
0.0
7100
Photon energy E (eV)
1.0
0.8
0.2
E0 -> 2839.6 eV
Photon energy E (eV)
1.2
1.0
0.4
0.0
2820
2850
RuSr2EuCu2O8
Normalized flourence yield If/Io
1.0
1.2
1.2
Normalized absorption intensity
Normalized absorption intensity
1.2
It is considered that the Fe-As layer in
RFeAs(O1−xFx) dominates the superconductivity. For this
reason, unoccupied state of Fe was studied by Fe-K edge
XANES spectra.
Fe K-edge XANEAS spectra of SmFeAsO1-yFy for
y =0.05, 0.25, 0.30, 0.35, and 0.40 were shown in Fig. 3.
The Fe XANES spectra are almost the same for the five
different F-doped samples, which may be due to intrinsic
properties, impurities, or the uncertain F-doping level..
The photon energy is much larger than Fermi surface
variation.
The angle dependence of Fe K-edge XANEAS
spectra of Sm0.95La0.05FeAsO0.85F0.15 [3] were shown in
Fig. 4. The Fe XANES spectra are similar for the three
different tilt angles. The shoulder at 7112.8 eV of Fe
XANES spectra is due to the contribution of 1s to 3d
quadrupole transition and 1s to As-4p hybridization state.
It is sharp as the polarization light parallel to the c-axis
and indicates that resonance between polarization light
and some directional states in 3d near the Fermi level
may exists.
Normalized absorption intensity
(115)
(006)
(220)
(113)(200)
(005)
(114)
(004)
(003)(110)
(111)
(002)
(001)
0
(001)
Intensity (arbitrary unit)
RuSr2GdCu2O8
(a) random powder
(112)
The grain-aligned powder RuSr2GdCu2O8 was
achieved by the field rotation method in applied magnetic
field ~ 0.9 T. A partial orientation of c-axis was
confirmed by x-ray diffraction pattern of RuSr2GdCu2O8
in Fig. 1.
Normalized absorption intensity
1
7140
Photon energy E (eV)
Fig. 3: Fe K-edge XANES and derivative spectra of
SmFeAsO1-yFy for y = 0.05, 0.25, 0.30, 0.35, and 0.40.
The discovery of high-Tc superconductivity in
RFeAs(O1−xFx) (R = La, Ce, Pr, Nd, Sm, Gd) with Tc ~
25-55 K has spurred a great interest to class of layered
oxypnictides (LnO)(MPn) (where M=3d metals, Pn=P,
As).
References
1. R. S. Liu, L.-Y. Jang, H.-H. Hung, and J. L. Tallon, Phys.
Rev. B 63, 212507 (2001).
2. C. Y. Yang, B. C. Chang, H. C. Ku, and Y. Y. Hsu, Phys.
Rev. B 72, 174508 (2005).
3. B. C. Chang, C. H. Hsu, Y. Y. Hsu, Z. Wei, K. Q. Ruan, X. G.
Li, and H. C. Ku, arXiv:cond-mat/0807.2833v1 (2008).
4. E. Z. Kurmaev, R. G. Wilks, A. Moewes, N. A. Skorikov, Yu.
A. Izyumov, L. D. Finkelstein, R. H. Li, and X. H. Chen,
arXiv:cond-mat/0805.0668v3 (2008).
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