X-Ray anomalous scattering study of a charge-ordered state in NaV2O5
Charge ordering of V4+ and V5+ in NaV2O5 has been studied by an x-ray diffraction technique using anomalous scattering near a vanadium K-absorption edge to critically enhance a contrast between the two ions. A dramatic energy dependence of the superlattice intensities is observed below T(C) = 35 K. The charge ordering pattern is the fully charged zigzag-type ladder with the unit cell 2ax2bx4c, but not the chain-type originally proposed for the spin-Peierls state. Charge disproportionation suggested in our model as the average valence V(4.5+/-delta(c)/2) is observed below T(C), showing continuous variation of delta(c) as a function of temperature.
Nakao
H
Neutron Scattering Laboratory, Institute for Solid State Physics, The University of Tokyo, 106-1 Shirakata, Tokai, Ibaraki 319-1106, Japan.
Ohwada
K
Takesue
N
Fujii
Y
Isobe
M
Ueda
Y
Zimmermann
M
Hill
JP
Gibbs
D
Woicik
JC
Koyama
I
Murakami
Y