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

4C, 16A/2004G041

Resonant x-ray scattering study of PrRu4P12Kenji Ishii*1, Satoshi Tsutsui2, Lijie Hao3, Tomoo Hasegawa3, Kazuaki Iwasa3,Youichi Murakami1,3, Shanta RanJan Saha4, Hitoshi Sugawara5, Hideyuki Sato4
1
Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute, Hyogo 679-5148,
2Japan Synchrotron Radiation Research Institute, Hyogo 679-5198
3
Department of Physics, Tohoku University, Sendai 980-8578
4
Graduate School of Science, Tokyo Metropolitan University, Hachioji 192-0397
5
Faculty of Integrated Arts and Science, Tokushima University, Tokushima 770-8502
Introduction
The filled skutterudite PrRu4P12 exhibits a metalinsulator (MI) transition at TMI ~ 62 K [1] associated witha structural phase transition with a modulation vector q =[1,0,0] [2]. A nesting of the Fermi surface at 2kF = (1,0,0)
suggested by a band-structure calculation induces
formation of CDW which is crucial for the MI transition[3]. However LaRu4P12 does not show the MI transition
although the nesting of the Fermi surface also suggested.
This fact indicates that 4f electrons of Pr areindispensable for the MI transition. Here we report on aresonant x-ray scattering study of PrRu4P12 at Pr L3-edge
to elucidate a modulation of electronic state of Pr. The Pr
5d states, which are intermediate states of resonant
process, are modified by the Pr 4f electrons through theCoulomb interaction and/or the lattice distortion.
Experimental
Resonant x-ray scattering experiments are performed at
BL-4C and 16A2 at Photon Factory. Single crystals ofPrRu4P12 were grown by a tin-flux method.
Results and Discussion
Figure 1 shows the energy dependence of Q = (3,1,3)
and (1,3,-1) which are forbidden above TMI. Thesereflections contain two components. One is non-resonant
component due to the lattice distortion, whose amplitude
is independent of the photon energy. The other isresonant scattering of Pr, which is enhanced near theabsorption edge (~ 5.955 keV). The existence of thelattice component is evidenced by abrupt changes inintensity near the absorption edge. Observed intensity is
an interference between both terms, and the interference
extends to higher energy beyond the absorption edge.
Because the resonant term for odd number of h+k+l
corresponds to the difference of anomalous scatteringfactor between two Pr atoms in the bcc unit cell, ourresults suggest a spatial ordering of two different
electronic state of Pr atoms.
Figure 2 shows the temperature dependence of theintensity of a superlattice reflection measured at bothresonant and non-resonant energy. The intensity at theresonant energy contains both components of lattice
distortion and the anomalous scattering, while that at thenon-resonant energy corresponds only to the former.

Quite similar temperature dependence at two energies
indicates that the lattice distortion and ordering ofelectronic state of Pr occur and evolve simultaneously.

Figure 1: Energy dependence of superlattice reflections
near the Pr L3-edge. In addition to the non-resonant
component due to the lattice distortion, clear resonant
feature can be seen.

Figure 2: Temperature dependence of superlatticereflection.
References[1] C. Sekine et al., Phys. Rev. Lett. 79, 3218 (1997).
[2] C. H. Lee et al., J. Phys. Condens. Matter 13, L45(2001).
[3] H. Harima et al., Physica B 312-313, 843 (2002).
* kenji@spring8.or.jp

Users' Report151