Successive jahn-teller phase transitions in Cs 2PbCu(NO 2) 6

Abstract

The sequential Jahn-Teller phase transitions in Cs 2PbCu(NO 2) 6 were studied by neutron and X-ray diffraction technique. In each phase we observed satellite reflections. The position of satellites in the reciprocal space is commonly given by k 0 = ( 1 2 1 2 ζ) with 0⪕ζ⪕0.5. In Phase II and Phase IV, the values of ζ are definitely determined as ζ = 0 and ζ = 0.5 respectively. In Phase III, ζ is not definite within 0.20⪕ζ⪕0.25 depending on samples, thermal cycling,etc. Phase III may be an incommensurate phase although there is the tendency that the value of ζ is locked in either at 0.20 ( 1 5 ) or at 0.25 ( 1 4 ).