Jahn-Teller phase transition in CsCuCl3 and CsCrCl3: A neutron scattering study

The diffuse scattering above Tc was studied in CsCuCl3 and CsCrCl3 by neutron scattering technique. These compounds undergo phase transitions associated with the Jahn-Teller effect. Their structures are characterized by isolated chains of face sharing CuCl6 and CrCl6 octahedra, respectively. The diffuse scattering shows two main features: it does not occur at the superllatice points of the low temperature phase, but is centred around the strong Bragg points, and its shape changes from one Bragg point to another. This behaviour, which is incompatible with critical scattering from intra-chain correlations of Jahn-Teller distorted octahedra, can be interpreted as “dense impurity” Huang scattering.